I have a 1 that works great and it is doubtful you'd find much meaningful difference between the versions. I'm going to go with the CLA recommendation. If the camera hasn't been CLA'd then it is pretty much certain that the prism foam has degraded and damaged the prism silvering. That is really not a big problem as the polished glass reflects well by itself. Polish the glass and feather the edge of the silvering with a mild abrasive such as toothpaste, and you won't even notice the damage. I believe having seen that an OM-10 prism will fit, but don't recall exactly. Either way, once it is fixed up it will be a joy for many years.