I've ordered them from China a few times. Once you get them you'll need to spend a couple hours testing all of them. The last time I ordered (40) and (6) were bad. I contacted the seller and he refunded me 15%. They appear to be old pulls from DIP sockets. I did not see any old solder on the legs.
Per the manual, an A2091 supports 100ns or lower DRAM. It is better to get the 60/70ns like you mentioned since you can use them other places - specifically if you update your A500 rev6+ mobo from 512KB to 1024KB. I *think* that requires 70ns or lower.
