Old Trak DRO Encoder Heads

A few months ago I picked up an old 2-axis Trak DRO. It's made by the same
people who made Trav-A-Dials, and uses a rotary encoder housed inside a
Trav-a-Dial like enclosure.

I've got all the pieces to install it to my Bridgeport. I even have the
control box, but someone removed the BIOS chip from the board, so that's
not useful at all.

Anyway, my question is how accurate are these type encoder heads? I don't
need high precision for my work, so if they are within .001 or .002, that's
good enough for me.

I'm planning on interfacing it to a PC probably with Tom's software/hardware.

Any tips or hints? Am I wasting my time with these heads? Thanks!