Hello folks! I picked up this Gruen Veri-Thin recently from the original owner. I quite like it! The dial is in amazing condition, and the crown is signed Gruen. It has a nice heft of gentlemen’s charm, and will make for a fun dress watch.

The only problem is that in some light the crystal is okay, but in bright light the mineral crystal’s true crazed-nature shines through. Does anyone know what the part number for a replacement crystal would be? The number in the case is 421-653. Many thanks in advance. I am told it is from 1950. I assume eBay would be my best source for the part, but I welcome any suggestions!






I don’t have the box, but just for fun, from an eBay ad (if it is to be believed), this is what the original box for this model would be.

 

Post the dimensions from corner to corner, vertically, and corner to corner horizontally, plus the width from 3 to 9, and height from 6 to 12, and I might be able to help you. Unable to help with a part number.

 

Thank you Canuck!
3-9 = 24
6-12 = 24.5
Corner to corner = 29.5

3-9


6-12


Corner to corner


I appreciate your help

 

No joy on the Gruen crystal. Close, but no cigar. It was worth checking.

 

Thank you very much for checking! I’ll move this over to WTB

 

Looks like it would polish out. Ask around about someone who knows how to go about it.
I've had excellent results with polishing acrylic crystals but mineral glass is a whole nuther story. It can be done though.
IIRC you need cerium oxide polishing compound for glass.

 

A PS to the above.
I've seen use of a dremil tool suggested but if it were mine I'd use the method sometimes used for lens polishing.
A dowel rod is bonded to the inside of the crystal with a glue or putty easily removed by soaking in acetone. (remember this is for mineral glass only not acrylic)
A stout cloth such as thin canvas can be stretched tight in a hoop like those used for fine crochet work.
A piece of plywood with a large circle cut out and the cloth tacked around the edges would work as well or better.
The compound is poured onto the cloth and using the dowel as a hand grip you then rub the curved outer surface on the cloth, which will naturally conform to the curve of the crystal.
With a rectangular crystal I suggest polishing in only one direction.

I don't know what grits to suggest.
This should work if the glass isn't surface hardened or heat treated.

Some types of glass are easy to polish while others are near impossible.

 

If you can borrow a digital caliper, and measure the crystal again, it might help. Or better yet, clean out the recess in the case, and measure using the same caliper. I have a cushion shaped glass crystal which fits a Gruen model ( the container in my assortment is marked for a Gruen) that is within about 0.5 mm in every dimension compared to the numbers you gave. It might be worth a look see. Be certain to reset the caliper to Zero before you measure. If you’ll do that, i’ll take another look at this crystal.

 

Thank you @Canuck ! I was looking on Amazon for a digital caliper, the reviews of their accuracy suggests that a piece of string and two Vienna sausages would take equally accurate measurements. Amazon Prime Day is on the 15th, so perhaps a good opportunity for me to step up to a better model at a better price. I have been wanting to get myself on YouTube taking about watches, so a purchase of calipers would get repeated use. Recommendations for caliper suppliers gratefully accepted. A long story made short, better measurements will follow ASAP

@Professor , thank you for your thoughtful message. I should have mentioned that the crystal has been polished as much as it can wile still maintaining some structural integrity. Your guidance lives on here for similar situations. Again, all my thanks!

 

Maybe i’ll Just pull one of these crystals (I have 3 of them) from my stash, and send it to you, gratis. You can try it. I think you’ll find it very close. I ave your address.

 

You sir are now on my Christmas card list! Thank you so much. Thank you also to the Mods for enabling this forum that helps so many.

 

I'm not sure which caliper you were looking at but I have found cheap ones to be quite accurate for casual use (maybe not for machining but certainly good to tenths of a millimeter). The last one I bought was a VINCA, https://smile.amazon.com/VINCA-DCLA-0605-Electronic-Fractions-Conversion/dp/B017KUC6XQ, it seems quite good for a $20 tool.

 

I find with my digital caliper, that it tends to measure about 0.2 mm small. I use it only for measuring watch case bezels, add 0.2 mm to the reading, then trial fit a crystal. I also have an antique analog caliper, and the closest you can get is 0.05 mm with it. For machining, I use my Mitutoyo micrometer, or a small metric caliper.

 

Thank you of course it is $89 on Amazon Canada . But I get the idea, many of those callipers are going to be close, many seem to have analog readings to double check

 

Are you looking for replacement or polishing?
If no luck otherwise, I can custom make a crystal for you, Need a case, shipping your case to me, however, is not an option, so I would need to find a case similair to yours, make the crystal on it, and send the crystal to you. Having a case at hand helps a lot for a perfect fit. An imperfect fit would collect dirt in the groove it creates.
The quality much depends on the material I can find, but generally not as high as what bulk producers make.
In rerurn and there is always something expected in return ha ha.I need a movement part which would cost you about €10 plus cost of shipping it to me.
This all starts to make sense when you realize no instrument is available to me for small payments due to my locality. Should you decide to give this a go, you can find a picture of a watch similair to your, to know what to expect and let me see the curvature.Regards joe

 

I will be sending DaveK a NOS glass cushion shaped crystal that is very close to the dimensions provided. Hopefully!

 

Thank you Joe! As Canuck posted, fingers are crossed that his en route replacement crystal will be a fit. If not, then your route seems intriguing - I have never heard of home grown crystals, but that’s pretty cool.

With gratitude,
Dave

 

If I recall correctly didn’t the old crystal manufactures catalog books. List crystals by make and model of the watch. On Gruen’s the numbers inside the case one set of numbers is the movement to other the case number.

At one time I had several old crystal catalogs dating back to the 1920’s I made a big mistake and let a friend borrow the crystal books. I never seen them again. I have not fooled around with crystals in a while.

The tough part is finding a crystal. With the real old mineral glass crystals if they have paper labels glued to the crystal good luck getting the etching off the crystal. Over time that glue eats into the crystal.

Good Luck

 

My late father was a Depression era watchmaker. During an era when there were no fax machines, no email, no internet, no computers, no on line material supplier catalogs. During those days, when the local material House was not able to supply a crystal, watchmakers often had to form their own replacement glass crystals. I’ve never done it, but I recall seeing my father making a glass crystal for a fancy shaped watch case. That was more than 50 years ago when he did that.

The process involved a sheet of asbestos, a 6” square of sheet zinc, a jewellers saw, a scriber, and (at the time), a naphtha fuelled torch. The general shape of the bezel was scribed onto the zinc sheet, and a jewellers saw was used to cut along the scribed line in the zinc. The shape refined with a file. Then, the sheet of zinc was massaged into a profile that matched the profile of the bezel. Then, each of the four corners of the zinc was bent downwards, and the resulting mould being placed on the asbestos. A glass crystal that was sufficiently large to cover the opening in the zinc, was placed on the mould. Then the torch was used to heat the glass crystal evenly and slowly, until is reached the melt point (not the flow point) at which time the new crystal dropped through the hole in the zinc, onto the asbestos beneath. It was allowed to cool, then the shape was refined until it fitted the bezel. There you have it.

 

If the crystal from Canuck doesn't work, try contacting GS: https://gssupplies.com/vintage/#

They have an online catalogue but, might be easier to call them as it is vintage. There are loads of GS crystals on eBay listed against case number but, probably easier to check with the company itself.

Cheers, Chris