Calibres 1620/1621 - A picture guide to the LCD Speedmaster variations

The Cal. 1620 Quartz movement

The cal. 1620, developed by Omega and SSIH (later to become SMH -see * below). Although it has only basic functions by today's standards, it is neverthless still a very accurate watch, capable of 0.15 seconds per day, or 5 seconds per month. This is better than a lot of quartz watches available even now. The very good accuracy is due to the high quality quartz resonator used, manufactured in-house by SSIH.

Specifications

Size:
The dimensions of this watch are 33.5mm wide (36.5mm over the pushers), 39.5mm long and only 7.2mm thick. The bracelet is a folded link type, with deployant clasp, and is integrated into the case. The watch weighs a total of 59 grams (2.0 oz) including the bracelet, and being so thin and light is all but unnoticeable during wear.

Functions:
The watch, by means of its single-row LCD display, can display:

• Time - Hours (12 or 24), Minutes and Seconds, and by a down-arrow Day of week.
• Time - Hours (12 or 24), Minutes and Date, as well as Day of week by the down arrow.
• 1/100 second Chronograph, able to accumulate up to 23 hours 59 minutes and 59.99 seconds.
• Split Second Chronograph (as above)
• Lap time
• Split/stop of 2 consecutive times
• Light source for illuminating the display at night, powered by a separate battery.
• Calendar programmed for leap years.

Display examples:

Time mode 1: Time with seconds, and day indicated by arrow. Display can quickly switched between Mode 1 and 2 (below) by 1 press of the top left pusher.

Time mode 2: Time with no seconds, and day /date displayed.

1/100th second Chronograph. All down-arrows flash when in lap/split mode and the chronograph is still counting.

Normal time and seconds display. The star indicates the chronograph is activated. If the star is flashing, the chronograph function is still counting seconds.

Today, one might consider the simple dial layout to be "classic" and many watches following this had (and still have) a similar look. As you might expect, the quality of printing on the dial (actually, the printing is on the back of the crystal) is superb. Not obvious from the pics is the Omega name and logo, which are a metallic mirror finish. The word "Speedmaster" is in red, and though this particular variation did not have the word "Professional" on the dial, some of the models in this series did. Why some did and didn't, no-one seems to know as the watches are essentially identical.

The main electronic and functional specifications are:

• Frequency of resonator - 32,768 hertz. High precision unit manufactured by SSIH.
• Q factor - 100,000
• Thermal coefficient - +/- 0.15 sec/day for a variation of +/- 5 deg C.
• Consumption - 5uA
• Running time - 20-25 months, depending on useage of light.
• Variation during wear - 5 seconds/month
• The display and lamp are powered from separate cells.

Changing the watch from 12 hour to 24 hour time is effected by moving a small jumper inside the back of the watch.

The watch calibre and serial number consists of a small (3mm dia) sticker bonded (in other words, glued!) to the circuit board.

As is often the case with quartz watches, setting them can be a tricky operation if the setting instructions are not available. This watch is no exception! Here is the full setting instructions for the cal 1620 :



The Integrated Circuit and Liquid Crystal Display used in the electronic module were manufactured by EM Microelectronic-Marin SA, a subsidiary company of Esa (Ebauches SA), or as we now know them, Eta. The liquid crystal display is still as good as the day it was made, while many contemporary Japanese ones have by now faded to being almost unreadable.

Source for above mentioned infos and pictures.

Watches with cal. 1620 (produced in the late 70s)

Now let's talk about the watches featuring the cal. 1620 and deviated from the cal 1620.



I will try to make summary about each model in this thread and to help you to spot each of them - as the thread grows, the first post will be updated with an index of models we discuss about and the links to each of them.

So far, I have referenced the following models and variations (some of them were available in steel and gold as variations) :

• 186.0002 (link)
• 186.0003 (link)
• 186.0004 (link)
• 186.0005 (link)
• 186.0009 (link)
• 186.0010 (link)
• Alaska IV Prototype cal. 1621 - unnumbered (link)
• Alaska IV Prototype cal. 1621 - numbered (link)

I will be adding the results of my research in this thread - I am gathering the information from here and there so can't pretend everything to be correct, if you find anything strange or wrong let's discuss it and update the posts - don't hesitate to participate 😀

Update : an extended part of my research has been made public in a dedicated website : http://www.omegalcdspeedmaster.com - I am thinking about extending the website with information about others models, keep an eye on it 📖

Ref:186.0002, Case No.386.0002, Produced around 1979

• Cal.1620 quartz movement
• Matt black dial with central digital display, day indication on silvered ground underneath digital aperture
• 36mm Brushed tonneau shaped case with screw down back Start/stop, split/light and lap/reset buttons at 2, 3 and 4, date-sec button at 10 and recessed set/select button at 8
• Integral brushed 1250/200 link bracelet with signed folding clasp
  
• Case, dial and movement signed

Ref:186.0003, Case No.386.0003, Produced 1977-1979

• Cal.1620 quartz movement
• Anthracite dial with central digital display, day indication underneath digital aperture
• 37mm brushed hexagon shaped case with screw down back. Start/stop, split/light and lap/reset buttons at 2, 3 and 4, date-sec button at 10 and recessed set/select button at 8
• Brushed 1299/266 link bracelet with signed folding clasp
• Case, dial and movement signed

Ref:186.0004, Case No.386.0004, Produced around 1979 for about 18 months

• Cal.1620 quartz movement
• Matt black dial with central digital display, day indication on underneath digital aperture, Speedmaster Professional Quartz under the day indications
• 36.5mm Moonwatch shaped case with clipped "Seamster" back. Start/stop, split/light and lap/reset buttons at 2, 3 and 4, date-sec button at 10 and recessed set/select button at 8
• Brushed 1305/741stainless steel bracelet with signed folding clasp
• Case, dial and movement signed

Some interesting notes from Chuck Maddox regarding the Seamaster casebacks on Speedmasters :

What is the background on the use of "Seamaster" cases on certain Speedmasters (most commonly Mark series, and c.1045 Speedmasters)? I assume it is because Omega considered these watches to be in water-resistant cases, but are these watches also considered part of the Seamaster line as well as the Speedmaster line?

Mr. Deithelm's reply:

* the case back of such watches are all showing the " seahorse " emblem, since all these watches were originally in the* SEAMASTER * line, although the official name of the Jubilee version is:
SEAMASTER - Speedmaster Professional 125 - chronograph

* it is only much later, when the " chronograph " vogue became so voluminous that we had to separate the sporty SEAMASTER watches from the " chronographs " and give them a separate line !

Hence, because the Speedmaster was considered part of the Seamaster line, they often sported Seamaster backs.

Fantastic stuff - keep it coming 👍

Ref:186.0005, Case No.386.0005, Produced around 1975-77

• Cal.1620 quartz movement
• Matt grey dial with central digital display, day indication on silvered ground underneath digital aperture, Speedmaster Quartz under the day indications
• 36mm Brushed cushion shaped case with screw down back Start/stop, split/light and lap/reset buttons at 2, 3 and 4, date-sec button at 10 and recessed set/select button at 8
• Original integrated bracelet ref. ST 1285.252.42 with signed folding clasp
• Case, dial and movement signed

The Gold-plated variation of the same watch features the same reference as well as case number, its caseback remains stainless-steel :

Cool write-up. thank you for your effort @kov. I didn't know you are so deep into vintage quartz Speedies (the mechanical ones I was aware of...;-)

I own 4 LCD Speedmasters (186.004, 186.009 and two prototypes) and since I got my hands on them, I realized there's a lot of small pieces of information here and there on the web but nothing "consolidated" available. The recent "Guide to the variations" posts from @Spacefruit motivated me to go through all of my personal notes regarding the cal.1620 and share what I have found about them so far. 😉

By the way, some of the members of this 1620 family are really freaking cool 😀

Thank you. I've updated the thread title however it's not fully right as some of the watches aren't Speedmasters. But since others are Speedmasters with Seamaster casebacks, I trust we can also allow ourselves a bit of creativity 😁

Great write up 👍

Just one comment, the 186.0004 isnt 39mm, its 36.6mm and 38.5mm if you include the button

Here are my reference points for the 186.0004 :



😉 (But not my pictures.)

Then mine is totally different to yours ....



And comparison to standard Speedmaster

Interesting, I will measure my own tonight and update. The pictures above weren't mine... Perfect, exactly the goal of the thread - thanks for your contribution. 👍

Ref:186.0009, Case No.386.0009, Produced around 1979

• Cal.1620 quartz movement
• Black dial with central digital display, day indication on underneath digital aperture, Speedmaster Professional Quartz under the day indications
• 3Xmm Square shaped case with clipped back. Start/stop, split/light and lap/reset buttons at 2, 3 and 4, date-sec button at 10 and recessed set/select button at 8
• Integrated stainless steel bracelet with signed folding clasp
• Case, dial and movement signed

Very seldom seen the 20 micron gold-plated variation of the 186.0009 Speedmaster :

Ref:186.0010, Case No.386.0010, Produced around 1979

• Cal.1620 quartz movement
• Brown dial with central digital display, day indication on underneath digital aperture, Speedmaster Professional Quartz under the day indications
• 3Xmm Square shaped case with clipped back. Start/stop, split/light and lap/reset buttons at 2, 3 and 4, date-sec button at 10 and recessed set/select button at 8
• Leather (?) bracelet with signed gold-plated buckle
• Case, dial and movement signed

Looks like this one is really very scarce - I could have found a very limited information and photographs on the web so far.

Does anybody here own one ? Any infos are more then welcome.

Thread bookmarked! 👍
Great stuff, thank you for the effort @kov !