Originally Posted by elemental

If by "ten speed" you mean it took a ten speed cassette (i.e. modern road spacing), it is 130mm. If it's a "classic" ten speed (2 x 5), it's probably 120mm. Modern track spacing in the back is 120mm, so most fixed wheelsets you come across will use this spacing and therefore fit the classic ten speed just fine out of the box.

What is this mystery frame? What does it say on it? If you don't yet have it, where is it coming from? It won't take much info to get a positive ID on the spacing.