Thanks Hugmenot, that's a fantastic resource.
So far I've worked out that I have a full copy of Workers & Peasants and a full copy of Red Warriors (minus one truck, which is practically a non-issue).
It looks like a copy of Heroes in here too, got the rules, maps 4 & 6 and the scenario book plus the countersheet, though the ILS looks like it has an error as the Luftwaffe should only have 7 leaders, there's an extra Lieutenant on the list that's been given the Major's statline (9-1-0/9-1-1).
Managed to find a scan of the marker sheet too, just missing a couple of demoralised counters and one that looks like a square wave with UC on the back (entrenchment maybe?), nothing that should affect play.
So that's three down, desperately looking for a scan of later edition information marker sheets (looks like AP switched to full color) so I can do an inventory of those.
The other mystery are these:
Look like homebrew counters, some are common units but some are marked "Sturm" 7-2 / 3/2 and "PSK" 2-5 6-0 (single sided). All Heer. No idea where they're from.
Slowly going to get there I think, at any rate it looks like I have enough to play a few scenarios, and I paid less than a full game. I'll definitely splash out on some newer titles if I get on with the system; more money to APL means more sweet, sweet War at Sea after all