It does look like an 86 Redline RL-20a same gussett but the lack of a chainstay brace rules that out. RL-20 Prostyler had stay stands. Maybe it was an Akisu for a department store bike like Pitbull suggested. Its not a diamond back for sure either. 90's DB's had stamps on dropouts and 80's Db's had diamond gusset. I'm clueless. Just ride it and enjoy it.