Gruen Case Serial Number to Date Tool....

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MikeTheWatchGuy
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Gruen Case Serial Number to Date Tool....

#1 Post by MikeTheWatchGuy » Sat Jul 08, 2017 5:06 pm

I've just launched a new tool found on the GruenWristwatches homepage and on the Serial Numbers page.

I got so much great feedback from people using the Style Number tool that I wanted to see if there were other tools that could be helpful.

This tool ATTEMPTS to combine the multiple tables that are required to find the manufacture date for Gruen cases. Each manufacturer has their own set of tables. Wadsworth has a couple. Star, Gruen, and others can be found on the Serial Numbers page. The tool simply does the table lookups for you.

As a verification, the tool will tell you the manufacturer of your case.

Do not enter any spaces.

The idea is to provide friendlier access to the data the the community has been working hard to fill in.

As with all historical research efforts, crosscheck your work at every opportunity. Find all of the dates you possibly can that are associated with your Gruen... Style Number Date, Case manufacture date, movement manufacture date and THEN make as informed of an opinion as you can make is my suggestion on how to use it.

If it sucks, there's a new "feedback" form on the About page that you can feel free to ignore.
If you like it, there's a new "feedback" form on the About page that you can use to send me praise ;)
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kastner
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Re: Gruen Case Serial Number to Date Tool....

#2 Post by kastner » Sun Jul 09, 2017 11:19 am

This is really nice Mike, thank you for all the effort you've put into it.

I find the serial numbers so fascinating and frustrating. I alternate between thinking that Gruen had a master code for it all, but then I'll look at something else and think "yeah, this is the same as where I work and things fall apart despite the best of intentions."

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MikeTheWatchGuy
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Re: Gruen Case Serial Number to Date Tool....

#3 Post by MikeTheWatchGuy » Mon Jul 10, 2017 9:59 am

QUESTION(s) on Wadsworth case serial numbers.....

The Wadsworth Case Serial Numbers decoding blew the doors off of the Gruen dating research efforts. It seems to be a highly accurate way of dating a Gruen's case.

Did Wadsworth RESET the serial number yearly???


A gross summary of the Wadsworth case serial numbers is that during the 1940s, the serial number was composed of a letter "G" followed by SIX digits. The first digit has a strong correlation with the year within the 1940 decade. And it seems like this was done on purpose.

If the first digit represented the year, that left the remaining FIVE digits to number the cases. That is enough to uniquely stamp 100,000 cases (0 to 99,999). If Gruen did not produce 100,000 cases in a year, then the upper digit wouldn't increment. I'm proposing the Wadsworth likely reset the first digit on a yearly basis so that this decoding scheme would work correctly and not require a lookup table.

Jack, did you keep track of the HIGHEST numbers you saw within each year? How often did the serial number nearly roll over or did it ever roll over?

We now know from the Curvex movement serial numbers that Gruen was selling maybe 2,000 Curvex 440s a year for the first 5 years as it took a while to roll over 9999. So, 100,000 cases is a LOT of cases for Gruen to ship. Also, Wadsworth did make cases for other people, did they reuse the serial numbers? Or are all Wadworth Case Serial numbers unique?
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JackW
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Re: Gruen Case Serial Number to Date Tool....

#4 Post by JackW » Mon Jul 10, 2017 11:03 am

Mike,

I'm please that you think the Wadsworth Serial numbers were an important component to understanding Gruen watches better. You were a big part of that effort.
MikeTheWatchGuy wrote:
Mon Jul 10, 2017 9:59 am
Jack, did you keep track of the HIGHEST numbers you saw within each year? How often did the serial number nearly roll over or did it ever roll over?
I did not save that data. I was focused on finding Wadsworth cases with inscribed dates on the back. Do I think Wadsworth made close to 100k cases a year for Gruen? No. Also, it appears that at first the serials did not roll over on an annual basis. G0 and G1 certainly cover more than one year. This was covered in the article to some extent.

Hope this helps with the work you got cooking.

Cheers!
All I know is based on hard work & writing by others. I can only aspire to augment this body of knowledge. If I am wrong it is because of my own failings. -me
"If I have seen farther it is by standing on the shoulders of giants." - Newton

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