I agree it is likely around 137ish. Don't bother looking for and paying the high prices for am original CampI axle just get a Wheels Manufacturing axle they are bit better.
Wheels Manufacturing Hub Axles
Ratz they don't make a CampI 137. I've used this 141 and cut it down because I resoaced my wheels for an 8spd FW at one time.
Wheels Manufacturing QR Rear Axle, 10mm x 26tpi x 141mm
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