So, I recently found an oddball sigma that I had to pick up - it's clearly a 70s model; greek letter above the sigma logo. The guitar is, unfortunately, missing the label from the inside, so I have no serial or model number. The guitar seems to be a DR or DM 7, judging by the body and headstock binding. However, the bridge is not adjustable. It's either a replacement bridge, or, like I said, an oddball model. Any ideas?