Radio code 1988 325i

[Box400]

Noob here. You know the drill.

Just bought a 1988 325i convertible that had been sitting for a while.

Sitting = dead battery
Dead battery = dead radio
Dead radio = looking for a hookup on the code

Pulled the head unit out & here's the serial:
F70813293

Can someone help a brother out, so I don't have to drive to the dealership?

Once I get deeper into this thing, I look forward to contributing rather than just asking for help.

[Box400]

Nevermind

Nice day, so said "screw it" to work, threw the top down and drove on up to the dealer.

Got the code, but the tape deck is screwy as it keeps wanting to either eject or autoreverse even though there's no cassette in there. Consequently no radio.

I wonder if those radio codes aren't crackable. If we could find enough serials and corresponding codes, we could see if there's an algorithm BMW is using. I'm no computer science guy, but I'd think it might be worth a shot.

Anyway, I've got an older Blaupunkt Toronto RDM126 head I'm going to try wiring up instead. Probably should have started there first.