I have been contacted by someone who kindly supplied some photos of their 510.501, which has identical markings, but with a different number... 82 AF 163. They couldn't shed any light on the history though, but this is a big find - it provided solid evidence that mine isn't a faked on-off!

Cheers
Stewart

: Thanks to NetMatrix (aka Paul) on here, I've exchanged a few emails
: with a mil watch expert based in South Africa.
: He (Neil) thinks that these markings could well be Kenyan Air Force
: (KAF).. or part of KDF (Kenyan Defence Force)..

: In 1st August 1982, there was a failed coup d'etat attempt to
: overthrow the Kenyan president. Lead by a group of Air Force
: officers (no aircrews), the failed attempt lead to the
: disbandment of the Air Force on 22nd Aug '82. It was
: reconstituted shortly after under tight Army control under the
: name '82 Air Force' (or 82 AF). It regained independent status
: beginning of 1994.

: The South African expert is aware of '82 AF xxx' markings on other
: mil issue items.

: Obviously, this is still speculation, and it could be coincidence
: that the markings are '82 AF', but it's the best lead I've had
: so far. So, if anyone has any other insights to add, please fire
: away.

: Stewart