The first two meters are my own, the MKII I bought between Christmas and New Year 2018, a brief write-up here:-
https://www.vintage-radio.net/forum/...d.php?t=152626 and possibly the most interesting out of the three Avo's pictured, as it appears be a January 1956 MKII, so quite early.
The second Avo is a Test Set Number 1, bears an NSN (Nato Stock Number) with brown/reddish Bakelite, as opposed to the MKII & MKVI's black bakelite/black plastic respectively. The meter has the metal backing and came with it's original instructions plus replacement leads. This was given to me by my then-manager, some 20 years ago. This meter also has the BLR121 battery converter, part number 5210-064, allowing me to use either a BLR154/V74PX/10LF54 15V battery, but since these are getting harder to find, 10x AG10's in heatshrink fit nicely.
The third meter, a MKVI, currently belongs to the company I work for, and has only recently gone out of UKAS calibration. I've been told on numerous occasions to either bin it, or take it home!
Fear not, it's currently in cupboard, under my own lock & key, used occasionally at work. Am contemplating rehoming this meter and replacing the red (rubber) markers behind the 'meter cut-out' & 'Rev MC'.
Serial Numbers:-
Avo 8 MKII 43148-C-156
Avo 8 Test Set Number 1 8048.570 (NSN 6625-99-105-7050)
Avo 8 MKVI 3031M90285 4/86
All meters were tested against calibrated instruments on Tuesday, all are in spec
Mark