Litschert Power Boosters were made to convert lower magnification 3/4", 7/8", and 1" tube scopes to 6x or 8x "varmint" scopes.
I've never seen Litschert Power Booster/Converter that was more then 8x. I have a couple of scopes that have them installed and think that they were sort of an era specific "patch" that was more "sizzle" then "steak". The idea being that you could unscrew the objective housing on your Lyman Alaskan or Weaver K2.5, screw on the Litscher unit, and go varmint hunting with a higher magnification scope. I don't recall ever seeing a Litschert unit with an AO feature, but the 5-10-15-20 might correspondt to 50-100-150-200 yards. I have some that are NIB, but they are buried in the totes in the storage unit, so it wouldn't be easy to get to them and see what the instruction sheets would tell us.
Jeff
