Identifying a Speedmaster 145.022-69 (Serial 27.7M)

Hi everyone,


I recently picked up a Speedmaster and I’m trying to make sense of the serial number. It’s a 145.022-69 with a "Straight Writing" caseback, but the serial number on the movement is 27,7xx,xxx


I’ve read somewhere that this serial range (27.7M) usually belongs to much earlier watches, but this one seems to be original and even has the steel brake on the movement. The dial is a painted logo step dial and the bezel is a DNN.

I’ve done a bit of digging and saw some mentions online about 'late assembly' batches or factory anomalies where certain serial blocks like the 27.3M or 27.7M were held back and cased later in the 70s. How do I find out more?
I'm trying to figure out if this is a recognized cluster or if I just have a bit of a weird outlier on my hands

I'm a layman when it comes to the deep history of these, so I'm trying to figure out if this is a known combination or if I have something unusual here. Does anyone else have a 27.7M serial in a Straight Writing case logged in their data?


Thanks for any help!

posting some pictures would help

Thanks Guys.

Serial no: 27,719,527

Thanks.

Intend on wearing it.

The mismatch is not bothering me at all. Was just curious as it is unusual.

Indeed.

Had it been fitted with a later serial movement I would've passed but, its earlier, copper plated and with the steel brake.

Also, watchfid mentions a batch of 27.7M movements fitted to straight writing case watches.

From their page:

"We have observed some 145.022-69s with earlier serial numbers, in 27.3, 27.7 and 28.0 mios, but their delivery is often in 1975 [or later], meaning that they possibly correspond to Speedmasters assembled later."

On speedmaster101's page there is a clear dead space in the serial range that had me curious:

145.022-68 (The Transitional): 26,550,000 - 27,320,000
145.022-69 (The Standard): 28,420,000 - 31,000,000