Cheers, I think I'll stick to eBay! I'll go for any badge, although any Edinburgh/Glasgow codes would be preferred
The letter code for the Scottish lowland traffic commissioner's area on PSV badges was MM (I don't think anyone's quite sure why the letter was repeated on all areas except for N - Metropolitan / London)
(LL was the Inverness office)
Broadly, it's not possible to state (unless the original owner of the badge has passed the information on with the badge) what badge numbers went new to which bus operator. The badges were issued in response to individual's licence applications so it would have been fairly random, although if a batch of licence applications were sent in the same envelope from (say) Glasgow Corporation, then those conductors would probably have got consecutive badge numbers.
But as far as I know, they didn't formally reserve particular batches of numbers for particular operators.
Some e-bay sellers will make very confident claims about the stuff they are selling, which is not always reliable. Some people seem to assume that buses only run in London and not in the rest of the UK, and that all London buses are / were routemasters...
MM conductor badges are quite common - only London, North West England and Lowland Scotland (and possibly Yorkshire) offices got into 6 digit badge numbers for conductors.
There's a couple of MM badges on e-bay with no bids at present, one - fairly high number, probably late 70s - didn't sell at 9.99 a few weeks back and has been relisted, one quite low number - possibly 1940s - as yet with no bids at 4.99.
I'd say £ 5 is reasonable, £ 10 tops. Less demand than driver badges, yes, but I wouldn't say "no demand".
The highest numbers in each sequence were not issued for real, they were the remaining stock (larger in some areas than others) when PSV conductor licensing was abolished (1981 from memory) which was sold off by the DoT on the enthusiast market a few years later. I think most areas' badges could be got for about 50 pence a go in the mid 80s...