ancient M16

[Rusty Lugnuts]

Hi I just stumbled onto a old m16, the person that i got it from didn't know the manufacturer and believes it to be a frankengun. There is some kind of a fire selector issue. When you turn the selector it seems too be on safe past where semi should start - almost like the selector plate isn't long enough. The first issue though is dissassembly, I can't get it apart ! I have taken off the stock, front handguards, mag release, the pin by the delta ring, another pin about the same size near the stock , the small diameter pin directly above the trigger and it's still rock solid. There are 2 more possible pins but i think that they are actually just for show. The trades on the gun say panther arms if that helps. What am i missing?

[Rusty Lugnuts]

UPDATE I have it apart now it was just ridiculously tight, I see a G&G marking up in the now uncovered top part of the body, So do selector plates come in different lengths?