Ok so maybe I was being stupid thinking that I could buy 5x MC12080 prescalers from China on eBay for £3.79.
If I order from mouser uk I would pay £3.99 each plus £12 delivery.
When I tested them, instead of dividing by 10,20,40 or 80 as determined by the S1,S2,S3 inputs, they divide by 2,4 or 8.
I suspect they are MC12093 devices.
A while ago I bought some LM4562 op amps from eBay. They turned out to have a GBW of about 4MHz instead of 55MHz.
I suspect they were really TL072 or similar.
I spent ages trying to figure out why my design did not work as expected.
I'm getting really fed up with being sold fake crap from China.
So I'm going to name and shame the sellers:-
'hia5' sells fake LM4562.
'gc_supermarket' sells fake MC12080.
AVOID!