Gubelin 5/10 mark, what does it mean? -Answered within!

Here is a question for anyone.

I have come across a Gubelin chronograph with "5/10" on the inside caseback. What does 5/10 signify?

First thought was that this could be number 5 of 10 produced. This thought doesn't seem correct in that there are several other Gubelins with the same 5/10. It is possible that a rash of watches that were the fifth in a series are all offered for sale, but unlikely.

Many of the 5/10 marked watches are 18K gold. But the watches are also marked 18k so it seems redundant and not likely the 5/10 indicated gold content.

They also have different movements and are not all round. The watch in question is a cal. 321 wheras others are not.

There must be a reason but I can't isolate a difference. There are other conjectures but therein lies madness. It is curious enough to be distracting. Here are some photos of examples:



Thanks for any help and sleuthing.

I've got a square cased Gubelin triple date moonphase, I just checked my photos and it has the 5/10 mark, too. No idea what it means but probably somehow related to Gubelin's trademark.

First thing, l'm jealous!

Trademark makes sense because it is near the logo, which is similar to the sqaure case in my pictures. The other round cases don't have the 5/10 near the logo like these two square.

Also, does the 5 look like an "S" in the square? I assume it's a 5 but maybe not. It's curious that the diagonal is connected between the logo and 5/10. I tend to not think coincidence when a label is involved and it is more than once.

Good thought, no cigar yet.

Thanks.

It definitely is a '5' to my eyes.

Holy Moly, Batman! You've got it!!!

I am impressed and grateful. I shouldn't be this excited about a seemingly trivial fact but I am. (Should I be worried?) Pretty good day.



Thanks again.

Dave

I think you would be lucky for their current after-sales-service staff to know what the marks meant. But you could try.