What does the I designation stand for ?

[Dan/Panther]

I was recently  having a discussion about the markings on a 1951 dial. The digit in question was the Capitol "I", or Roman Numeral "1", The consensus was that the digit stood for the first quarter of the year, as the dial was dated 2-51. Well I was working on my 51-501T tonight, and noticed the same digit on my dial, however it is dated 8-51, so that kind of rules out the first quarter theory, Now what does the "I" stand for ?
I vaguely recall awhile back hearing or reading that early on the color Black was designated 1, does anyone else recall that ?
D/P

[Dennis Markham]

Dan, I don't know the definitive answer to your question.  One thought I had was that like the earlier model 302, the I stood for Indianapolis.  A was for Atlanta, S for Shreveport, etc.  But I've never seen a 7A with anything other than an "I".  Good question, thanks for posting it.  Perhaps we'll find out for sure.

[Jim Stettler]

It could stand for the shift.
Just a guess.
Jim

[paul-f]

When this has come up in past discussions, the best guess has been Indianapolis.  AFAIK there's been no proof found.  A number of us have looked through lots of BSPs without finding it described.

"I" seems to have appeared on bottom plates, dials and several other components -- but wasn't reliably there. 

-3 was the color code for black decades before the 500 set came out.

[Dan/Panther]

Just doing what I do best, being the devils advocate...
If the "I" stood for Indianapolis, then what does the Roman numerals "II & III" stand for on 302 dials. Kind of confusing if "I" stands for Indianapolis, and II stands for 2nd quarter, and III stands for 3rd quarter, and IV stands for 4th quarter, what would be used for 1st quarter ?
D/P

[paul-f]

It seems to me that the I in this case has nothing to do with date marking, as there's no year following it, as was done before months were marked. 

Why would a quarter code be needed if the month and year are marked? The date is marked in MM-YY form.

However, there were later components marked with a 1, which are obviously not Roman numerals, but could be a shift code.  Has anyone seen a 2 or 3, as we see on housings?