I have 10 I can sell but have no idea what the going price is
You could use recent coins as an example, I'll lay out two examples for you.
Franko is .25 per block. FTC is 200 per block.
10 Frankos would be 40 blocks worth of work, or (200*40) 8000 FTC. Today's going rate for FTC (keeping in mind it is has come down a lot from its peak) is 0.00124 FTC/BTC.
So considering 10 Frankos to be equivalent to 8000 FTC (considering block size only), it would work out to 8000*0.00124 or roughly 9.92 BTC.
Franko is .25 per block. CNC is 88 per block.
10 Frankos would be 40 blocks worth of work, or (88*40) 3520 FTC. Today's going rate for CNC (keeping in mind it is has come down a lot from its peak) is 0.0009 CNC/BTC.
So considering 10 Frankos to be equivalent to 3520 FTC (considering block size only), it would work out to 3520*0.0009 or roughly 3.168 BTC.
Note that there is a pretty big disparity between those two example coins. You can do this for a few other coins as well, but it should give you some idea of value. I am not going to determine which is right, but it does offer some guidance.