Just a thought, the slide rule is only really of use if you are away from your nav bag and you have brain stall.
If you are fast jet just think, 180gms of wristwatch at 7 g is, let me see - 18 against 10, look at 7 on the inner ring and it is 1250 on the outer. Now in English that is 12.5 on the outer against 10 on the inner then read against 22 on the inner is 274 on the outer.
Now where were we? Oh yes, somewhat over a kilo under 7 g, or about 3 lbs.
Just don't try and look at your Breitling under 7gs.