There's a lot more to what cigarette smoke does to a receiver than smell.
It gets into every control, key and contact. I bought an NRD-525 that must
have been exposed to smoke. Several of the keys won't make contact, all the
variable resistors are noisy and it's just about unusable. About the only
thing that can be done is to replace the bad resistors and switches and
clean all the contacts. Not a small job.

John Reed

Dear Colin,

If the seller is local to you, you can go over to his house and try the
radio for yourself. If the radio was well-taken-care-of, there should
be no problems.

Cigarette smoke does not cause any real damage to radios. The tobacco
odor will dissipate over several weeks and should be totally gone in a
year or less. If you're really concerned about the odor, leave the
radio outside for a few hours each day (in nice weather only!). That
should accelerate the dissipation of the odor.

Best,

Joe