Universal Geneve Watches On Ebay

Posts
170
Likes
386
https://www.liveauctioneers.com/item/31983903_universal-tri-compax-full-calendar-ref-22258-around 😁

I have 6 examples of reference 22258 and 59 between 946.791 and 997 in my database so I assume a batch of somewhere between 250 and 500 pieces.
If you assume that there was one watch of the same model for every serial in the given range, then I think you can treat this like a modified "German Tank Problem" with an unknown starting serial, and this says your estimate for the total should be:

(max_observed - min_observed) * (1 + (2 / (num_observed - 1))) -1

i.e.


In the case above this would yield an estimate of 288 total.

(I'm not quite sure why you can't model it as estimating the bounds of a discrete uniform probability distribution from which you have selected at random, but doing so seems to give slightly different results. 📖 )

Edit: missed some parentheses originally...
Edited:
 
Posts
13,461
Likes
52,951
There's a few sub 1,000,000 serial in Sala, including a 946,XXX so I guess not unknown
Indeed. This is an early case as evidenced by the protruding corrector buttons. I find in interesting that the moon face isn’t shown.
 
Posts
6,282
Likes
9,839
If you assume that there was one watch of the same model for every serial in the given range, then I think you can treat this like a modified "German Tank Problem" with an unknown starting serial, and this says your estimate for the total should be:

(max_observed - min_observed) * (1 + (2 / num_observed - 1)) -1

In the case above this would yield an estimate of 288 total.

(I'm not quite sure why you can't model it as estimating the bounds of a discrete uniform probability distribution from which you have selected at random, but doing so seems to give slightly different results. 📖 )
Interesting. I am aware of this approach but it goes a bit above my IQ 😀

I only recorded the case numbers if the movement number was also known. With some (read: perhaps a lot of) digging more serials may be found.
 
Posts
33,232
Likes
37,957
Interesting. I am aware of this approach but it goes a bit above my IQ 😀

I only recorded the case numbers if the movement number was also known. With some (read: perhaps a lot of) digging more serials may be found.
Yea this bloke may be excessively intelligent to be hanging out on an internet watch forum with a bunch of degenerates. Very interesting approach through.
 
Posts
6,282
Likes
9,839
The German tank problem is one of these very intruiging WW2 things 😀
 
Posts
13,461
Likes
52,951
If you assume that there was one watch of the same model for every serial in the given range, then I think you can treat this like a modified "German Tank Problem" with an unknown starting serial, and this says your estimate for the total should be:

(max_observed - min_observed) * (1 + (2 / num_observed - 1)) -1

In the case above this would yield an estimate of 288 total.

(I'm not quite sure why you can't model it as estimating the bounds of a discrete uniform probability distribution from which you have selected at random, but doing so seems to give slightly different results. 📖 )
Ok .. play time..is “num observed” = “Max observed - Min Observed” ? Thanks
 
Posts
170
Likes
386
Ok .. play time..is “num observed” = “Max observed - Min Observed” ? Thanks
Using @Mark020's numbers:
I have 6 examples of reference 22258 and 59 between 946.791 and 997 in my database
max_observed = 946,997
min_observed = 946,791
num_observed = 6

The proof in the PDF is a little bit beyond my abilities too, btw; I only play a mathematician on the internet.
Edited:
 
Posts
6,282
Likes
9,839
With the one I posted above it should be 7.
 
Posts
6,282
Likes
9,839
I think 22258/9 were made in multiple batches. I have more records - again only: if I have both serial and movement number - than the 6 I mentioned.

However the first batch is all in the range I posted above. So:
Batch 1 946k
Batch 2 1.043m (around)
Batch 3 1.066/1.067m
Batch 4 1.156/1.157m

Total records: 12 of which 9 22258 and 3 22259. The one in Sala is also 946.xxx but unfortunately Sala rarely shows movement pics.

My database started as a fun project but is now a - kind of - addiction. Now over 700 records of serial and movement from app. 700k to 1.9m serials. I will write something about it when I know what I discovered
 
Posts
170
Likes
386
I think 22258/9 were made in multiple batches. I have more records - again only: if I have both serial and movement number - than the 6 I mentioned.

However the first batch is all in the range I posted above. So:
Batch 1 946k
Batch 2 1.043m (around)
Batch 3 1.066/1.067m
Batch 4 1.156/1.157m

Total records: 12 of which 9 22258 and 3 22259. The one in Sala is also 946.xxx but unfortunately Sala rarely shows movement pics.
I see. The 274 estimate should be pretty reliable for Batch 1 then, and you could use the same method to estimate the other batches individually.
Edited:
 
Posts
6,282
Likes
9,839
Batch 4 also points to 250, batch 3 to 500. I wont be surpised if these references were made in batches of 250/500.

Another interesting reference - because high number of samples - is 32407 which was typically used for Uweco and Berthoud (13 samples)
Batch 1: 799k (4 samples). Tank number: 614. However: the movement numbers are much closer: within 150. TN based on movements: 226
Batch 2: 834/835k (4 samples). TN: 407. Based on movements: TN 436
Batch 3: 842/842k (5 samples). TN: 1.429. Based on movements: TN 8.099

I'd say that batch 1 and 2 were both 500 pieces and batch 3 1.500. Total production 2.500 pieces.

Yet another: 22209 (total 11 samples) gives the following challenge.
Batch 1: 873k (2 samples). TN: 19. Based on movements: TN 236
Batch 2: 875k (2 samples). TN: 137. Based on movements: TN 239

Or:
Batch 1: 873/875k (4 samples). TN: 3.101. Based on movements: TN 1.822

So: some work to do here
Edited:
 
Posts
6,282
Likes
9,839
Just for the fun of it: ref 31250 (the famous Wilhelmina which is no Wilhelmina). 15 examples.

TN on serials (878-892k): 15.774
TN on movements: 12.316

Another one: 31.230 (11 examples)
TN on serials (1.029-1.032m): 3.866
TN on movements: 16.716

Interesting results
 
Posts
170
Likes
386
Just for the fun of it: ref 31250 (the famous Wilhelmina which is no Wilhelmina). 15 examples.

TN on serials (878-892k): 15.774
TN on movements: 12.316

Another one: 31.230 (11 examples)
TN on serials (1.029-1.032m): 3.866
TN on movements: 16.716

Interesting results
Those are fairly big ranges. Do you expect that every consecutive serial from, say, 878-892k was the same model? Does your database not have any other models with a serial in that range?
 
Posts
6,282
Likes
9,839
Nope. Just these
 
Posts
4,757
Likes
12,034
(I'm not quite sure why you can't model it as estimating the bounds of a discrete uniform probability distribution from which you have selected at random, but doing so seems to give slightly different results. 📖 )

Edit: missed some parentheses originally...

The PDF you linked is essentially doing this. However, the statistics you are using are the max and min of a sample of size N taken from a discrete uniform distribution. The statistics themselves do not have a discrete uniform distribution. The estimator in the classic GTP is a moment estimator, because the maximum likelihood estimator for the number of tanks is not very useful (it is simply the max observed serial #).

We can continue this discussion over private message if you like. I am familiar with the GTP, but I have not worked through the details of the mondified GTP that I presume are in the appendix. It might be fun to go through it.
 
Posts
218
Likes
743
This is deep. I despised stats class. I’m here for the watch pr0n! 😝
 
Posts
6,282
Likes
9,839
Well: pr0n wise I missed out on this one https://www.ebay.nl/itm/184697916963?ul_noapp=true
Description: #52203, #1069320. The 17 jewel movement is also signed Universal Geneve & Swiss. It is #235965.
Somebody did a nice deal here I think

 
This website may earn commission from Ebay sales.