Joseph, the Rangers were made from the late '60's-'70's, mostly for school archery programs (gym class), and "Lane shooting" (yes, bowling alleys). They were made using early '60's Grizzly forms with no tip overlays. Quick mass production, cheap, and easy, yet some of the heavier poundage ones were excellent shooters, and there are unique ones that are cool to collect. If you can find one in the 40#+ range, you will have a great shooter.
The "5" indicates a general weight range, most of the time numbered from 1-5 with 1 being the lowest. That way you could just grab whatever number you were used to shooting and head out. With the fact that yours is missing the actual weight under the plate, you will have to scale it.
Like I said, the ones over 40# are very underrated bows and severely overlooked when in good condition. Most of them were extremely abused by students or inexperienced individuals looking for some fun. I would say a majority that did make it are either still in some school's storage facility or a landfill somewhere.
Some came with medallions, some with a sticker, most with nothing other than a silkscreen and a 1-5 number.