1. When I first got this rule I though it was rather ordinary but it actually has a few interesting features.
2. Although clearly intended for the English speaking market (it has a measurement scale of inches) it names the scales with their German commercial equivalents:
K - capital
Z - interest
T - time in days
E - Purchase (Einkauf)
V - Sales (Verkauf)
3. The upper scales are displaced by 360 (not the more normal p or Ö10) relative to the lower. This ties in with the Faber Castell 52/82 which uses a cursor with 360 displacement for daily interest calculations.
4. The cursor on this rule has a line for dividing/multiplying by 12, for pence and shillings perhaps. Unlike the Faber Castell it does not have a line for basing calculations on 365 days a year.
5. The rule is not listed by Peter Hopp - which makes it a rarity.
6. The rule, number 7/52, and the Faber Castell 52/81 were both commercial rules. Is it a coincidence that "52" appears in both model numbers.
7. Although there were no scales on the back of the slide, the back of the stock had the usual cut-out for such scales.