It would appear to be a 5 speed fully synchronized transmission, with bell housing integral to aluminum transmission case. It is similar in design and appearance to HM290, 5LM60, and NV3500 (New Venture) series transmissions, but slightly smaller. Requires some special tools to rebuild. Used in 1998 and up GM S10 vehicles with 4.3 liter engines. Also known as an M50.

Regards,
Glenn