There is some kind of jumper you have to set to select either AUI or
thinwire. It should be close to the AUI-connector. I do not have
a card available to look at but there is an illustration in the manual.
It seems to be a rather big thing. If I recall correctly it is blue.
Hope this helps.

Anders

P.S. I have no idea if changing that switch will change the drivers idea
of what interface you have. It may still call it 10base5.