Thanks for that. The seller has just confirmed that he thinks they're the same, and that he'd be happy to take it back. So I've bought it. He's described it as great condition. He sells many old Mercedes parts, so hopefully he would have noticed a leaky box.

Mines been leaking for some time now and it's recently got bad, and stiff when turning right.
I'll keep the original and get it reconditioned if I can find someone that does them here in the UK.

Thanks for the help.