Funny - this thread also features a Puch Marco Polo from the same era. The bike in question here is a 1976-77 model with a 3-tubes 531 double-butted frame and the same Bocama Professional lugs and forged Shimano dropouts as the full 531 Royal Force and Royal X; for that matter, the 1976-77 Austro-Daimler Vent Noir, as well. Zero braze-ons except for a pip to keep the shifter clamp from sliding down the downtube. The forks and stays are Puch 2600, their own brand of chro-mo tubing, as opposed to hi-ten or something lesser. Here's the catalog for 1977.

Loads of room for at least 32 mm tires - I ran my Royal Force with full-size 27 x 1 1/4-in tires and Bluemels fenders in the late 70s. DO check the wheels, because if it is a U.S. market Puch the stock wheels would likely have been 27s and 700C. It will also likely be spaced 120 mm in the rear rather than 126 or 128.

IF you like it and it fits, it should ride nicely when serviced. They took a lot of pride in precision mitering the tubes and silver brazing them up. They're not terribly common in the U.S., and the first couple of years, especially. I think they came in just in time for the great Bike Boom to peter out.

Here's mine, the next model up in 1976, discontinued in 1977, and purchased new in 1978.