That's a different scale altogether Justin. You are correct, the old Ohaus 505 was a two poised scale, almost exactly like the M5 except that it had the big aluminum pan and wire pan support and didn't have the auxiliary weight . An excellent scale and can be updated with a later style pan and pan support to make it more convenient to use.Some of the old 505's were two poise, they looked like the M5. Mine is red and creme colored.
The later, new style, 505 was a three poise and the 502, using the same body, was a two poise.