Bear Mag TD's generally run in the 200-300 category.
The serial number for the riser should be stamped on the tang in the upper limb pocket.. It will start with A,B or C. That of course is the riser model as well.
The serial number for the limbs will start with 1,2 or 3, and likewise that is the length of the limbs.
A riser and #3 limbs make a 60" bow as does a B riser and #1 limbs
The limbs should be marked with the draw weight for the various risers as well