BR3 valve body calibration stock?

[ddevito]

Picked up a 200-4R no tag on tail end pulled pan to see at first an "AK" further disassembly realized it was not actual coded side which had a barely legible "BR3"
how do I verify valve & spring calibration sizes for BR code . also what is the AK stamp in yellow on passenger side? I have several CQ & CZF's one OZ never seen both sides
stamped .

 

[ddevito]

realize this thing is modified has 3 small Allen head plugs ,may go to part sale board ..maybe some can figure out mods not me