[Coco] CoCo 3 ROM - MXP-0986 ???

[sales at gimechip.com]

In one of my old broken CoCo 3 MOBO's with a 1986 GIME, the ROM has been replaced with an EPROM labeled:
MXP-0986
26-334
O/S 8323
12/18/91

Anybody have any idea what this is? It seems to just be a modified CoCo 3 ROM, but I wonder what it does?
-John