While the 1973 P-13 would have come equipped with tubular 700c wheels, it would not be unusual for the owner of a P-10 to upgrade the 27" clinchers to a tubular wheelset. In fact, if the bike was ordered at the Schwinn LBS (as opposed to being on the showroom floor), the customer could have easily specified tubulars at that time.
I bought a '71 P-13 frameset about a decade ago. Originally I had a set of 27" clinchers (that just barely fit). I eventually found a set of vintage Hi-E hubs/Fiamme rims tubular wheels and oh how the ride is exquisite! Keep an eye on ebay, CL and the C&V classified for good deals on vintage tubular wheel sets. Even if they don't have the Campy high flange hubs, they will be worth the effort.
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Bob
Enjoying the GA coast all year long!
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