This is the SST27SF512-70-3C-PGE 28 pin DIP chip (from old stock).
The speed is 70ns, it is much faster(better) than 90ns chip(SST27SF512-90-3C-PG) and 150ns chip(SST27SF512-150-3C-PG).
You can directly use this 70ns chip to replace the all other lower speed EPROM chips. Such as automotive ECU tuning.
It can be used for drop-in replacing: all brand 27C512, AT29C256 (set offset at 8000 when programming).