Originally Posted by FBinNY

Judging by the spacers (and my faded memory) this is a 126mm hub set up for a 6 or 7s spin-on freewheel.

The OP shouldn't rely on me here, but measure the axle over the locknuts, and the distance from the RH locknut face to the freewheel shoulder. For 6s o 7s, the shoulder to locknut width will be roughly 32-34mm. For a 5s it'll be closer to 27mm. Note that 7s requires 1-2mm more clearance than 6s (narrower spacing)