Help with 250 ID

I just got a 250 motor and frame. It is a wide case with DM250 stamped on the left front motor mount boss. No other numbers anywhere on the case except the numbers NM15000390 stamped on the left side top case behind the cylinder and on the frame neck. I believe these numbers to be issued by the state of New Mexico for the purpose of "lost title" retitling. I could not fit these numbers into any online sequence I found. The frame has a battery mount so perhaps a Monza frame? No numbers or sticker. If a pic would help I can post tomorrow.