I received feedback from Futurlec, a picture of one of the 41256 chips.
This looks good, so I have will order them, and wait until they arrive.
To upgrade my Amiga 500 (rev 5.) to 1 Mb chip ram I need an A501 extension board or 16 ram chips.
As I can’t find an extension board, I started to look for 16 4256 or 41256 fast mode dram chips.
on Ebay I can find them for $2.50 per piece (so totaling $40.00 without shipping), this is to expensive for me, so I continued my search.
I found some shops that still sell them, but most are in the same price range (or charge high shipping costs for shipping to Europe).
But I seems to find one place now, but I’m not sure if this are the correct ones.
I send them a mail, asking for the brand, so I can check the datasheets
Check the Futurlec website, the part number seems correct, and for $0.95 per piece.