I have a Petri in M42 but still no glory for an exact ID. I really want to use this lens. I think I am going to buy a Cheapo Macro Tube kit and use the last ring as a Mount for my Camera. Going to be a Cobbled mess, but I think it will work. If I set the lens to Infinity and slide the lens forward until everything is sharp and in focus. Next I will make a mark and make some sort of permanent mount out of the macro tube extension.