I can only find a couple of references:
"Mercury KM266 FDMxL + Duron 1800 (S,G,L) - All-in-one solution with an AMD Duron 1800+ which is flashed to a Pro 3600+ Processor. Amazing value for money with almost everything you need included"
This one does not inspire any confidence in me... but it may be a well known procedure.
click here= for an ebay item.