Setting a price for Spica TC50s

Try tightening the screws for the drivers. May be the source of the buzz. 

I have seen these for sale on AG’s marketplace. Don’t remember asking price.

Spica TC-50s in excellent shape are getting about $250-$350. Maybe a little more if you have the original box and packaging and manual.

The ones you have, in the shape you state, would be worth probably $100-$150, if you could even sell them.

Most people who are looking for vintage gear, want said gear, in perfect shape.

Or at least w/o any significant operational defects.  If one of the drivers is damaged, the value would be largely for parts.  Actually, some have found that vintage speakers in particular, are more valuable if parted out.  Not that I'd advocate doing that if the pair had no operational defects. 

The foam surround on the Spica woofer is known to rot (perhaps the cause of your buzzing), and I don't believe that exact woofer is still available. A replacement woofer would most likely require a change in the speakers x/o. Collectors of vintage speakers for that reason buy extra examples, just to have spare parts, as do restorers of vintage automobiles. I restore vintage drums, and buy damaged drums just for the parts.

If the surrounds are damaged, they can be replaced. At a cost of ~$30/driver.

These speakers, as is, are probably only worth $150, and only to one who already owns a pair and wants backup parts, or one who wishes to recondition.