Google says the Mercury 3600 is actually the Teco Relisys VM3582
. According to the sane database (see my sig) some relisys scanners are supported, but yours isn't listed.
If you're brave, you might try one of the sane-teco drivers and see if any of them are able to drive it, but that runs the risk of damaging the scanner. Your best option is probably to replace it with something that's known to work.