This Sigma model is closely related to Ricoh XR-7 and Sears KS-2. They all have a Pentax K mount. SA-1 has two handle pads for your right hand, and has the AE lock on the front right hand pad (easier to use with right hand only). However, SA-1 has no multiple exposure although the DOF levers. on the three models are the same.
Its build quality is very good.