DEKAPOT model differences

[munorc]

In looking though a box of panel meters, I found a surpise, a Dekapot model X537-1.

In looking at past posts, I see some discussion of these.  IET Labs still sells the DP-1211 and DP-1311 and has spec sheets posted.

This unit is labeled Voltage Divider, Resisistive, Decade.   The DP-1211 and DP-1311 are labeled Kelvin-Varley Voltage Divider.

ESI seemed to have pretty broad range of model numbers and there does not seem to be any pattern to them, i.e. X537-1 vs. DP-1211.

Does anyone have specs beyond what I find for the DP-1211 and DP-1311? 

Internally, are these similar or are they different designs for different purposes?

[PedroDaGr8]

The Stock No implies something Military or Federal Government related as the PSC/FSC/NSN code for resistors starts with 5905. It would likely have an NSN of 5905-00-445-2551 or 5905-01-445-2551 (neither of which turn up anything).

[munorc]

If so, perhaps the 42 in the serial number is a year code. It differs slightly from the rest of the number.

[lowimpedance]

It does appear a much older style than the unit pictures in my 1974 ESI catalogue. No Mention of that model number and the 'DEKAPOT" name only refers to the KVD DP1211 and 1311.
My guess is its most likely a DP1311 and the the 1K input resistance is also consistent with values listed in the catalogue. Testing would be needed to confirm or not.