Axle/gearbox ratio

I’ve just got a 1968 Daimler 250 auto (BW35 I guess) and I’m a bit puzzled about the gearing.

I can’t detect more than one gear change from rest, and I have tried with the selector lever in D2 and D1.

Also, when cruising at about 50mph I get 2800 indicated on the rev counter, which I think is higher than it should be.

I don’t know much about this car yet so any information anyone can provide would be very useful.