Flag EP found - but where's the album...?

The latest addition to my covers collection arrived today - it's one of those elusive 7-inch EPs on the Flag label, which trailer the World Top 12 albums. Alas, there was no picture sleeve with this copy, but here are some scans of the record (click to enlarge):

This particular EP is unusual in that none of the six tracks are known on the associated album series, and so the recordings can only be heard on the EP, making them particularly rare. In all other cases I know of, the EPs are entirely or predominantly linked to a specific LP, so this is an odd one out - although I acknowledge that my listing might be incomplete.

How many of these EPs were released? It's impossible to know, but so far I have documented nine, one of which is completely unrelated to the LP concept:

• EP number 10 - tracks mainly from LP volume 34
• EP number 11 - tracks mainly from LP volume 34
• EP number 12 - tracks mainly from LP volume 3
• EP number 13 - tracks all from LP volume 35
• EP number 15 - unrelated EP of Hawaiian Hits
• EP number 16 - tracks mainly from LP volume 35
• EP number 21 - no associated LP - see above
• EP number 23 - tracks mainly from LP volume 36 
• EP number 25 - tracks all from LP volume 37 

It seems unlikely they were released in a continuous run; check out EP 13 for instance, which has half of the LP volume 35 on it; come EP 23 they had only progressed as far as the next LP, so where could all those intervening discs have come from?

I would love to find out more about this EP series - please contact us if you know anything else about them. Meantime, here is a gallery of the discs listed above (except number 10, which I don't have an image for). Note how the unrelated EP has a completely different label design: