That looks familiar, like an early to mid 70's vintage, and yep, it's a loop scavenged, baffled piston, and should be 2 rings...
They're good, long running engines, just take your time and break it in carefully, and use fuel with plenty of castor. I would say no more than 10% nitro too. An 11x7 or 12x6 prop and a Fox long plug w/ idle bar works well...
Don't expect modern day standards performance, but for sport flying, it'll work well, and last a long time. I "inherited" a couple that my childhood "mentor" left me before he died that must have (I don't know how many) hundreds of flights on 'em...