Question regarding Victor Concert Reproducers

[Ripduf1]

H=I have a question for the Victor Experts out there. I just came upon a first for me and I have been collecting for about 20 years, it has to do with Concert reproducers. I know that Eldridge Johnson Concert reproducers had longer throats than Victor Concerts. But I made the following observation today, My EJ ser number 8686 is a sixteenth taller in length to my Victor Concert 18521, not a big difference at all. However I have a Victor Concert serial number 58175 that is a quarter inch shorter (1.25 vs. 1" throat) than both the EJ and 18521 mentioned above. Really noticeable!
Can anyone confirm a transitional serial number where the Victor Concert long throat became not so long? I speculate that this had to do with the move to screw on brass elbows (hence the shorter throats) vs slip on elbows (longer throats) the serial number sequence would seem to confirm that chronology. Has anybody realized this and can confirm this is indeed what was happening back then and a transitional ser number?

More minutia. John

[pappde]

I have two Victor Concerts. I also have noted the difference and assumed the same reason behind it.
#31284 throat @1 and ¼"
#65706 throat @1 and 1/16"
I also have a British edition Concert with #23857 @ 1 and ¼"
Denes

[Ripduf1]

So we now know the transition is somewhere between my 58175 for 1" (Shorter)
And
your 31284 for the 1.25" (longer).

With a few more samples we can nail this this week! Can others please check the length and serial number and please post results here?

Thanks in advance

John