Looking for RCA 121540 Transistor replacement

I'm looking for a replacement for q RCA 121540 Transistor . I know RCA used his own part numbers and i asume there is a replacement in the normal jedec series or something but i can't find the right cross-reference. The transistor is used in an old Altec-Lansing 4 channel Cinema amplifier. And i very much would like to give the public the surround channel back.

I've tried and tried to find this component, without any luck. I just wanted to let you know that we're not ignoring you. Good luck!

It's possible that the number is simply an 'in-house' one used by Altec-Lansing. What does the transistor actually do in the amplifier?, and do you have a circuit diagram for it?.

in the SK SKG202E cross guide(1986) it lists "121540 altec lansing" as SK9033 or ECG 60
to-3 250w 20a 140v
Good call on reminding of in house numbers.
I also was searching for the standard RCA numbers.
Doug