wing nuts: is 3/8 axle typical
 

Just curious after noticing 3/8" wing nuts and solid axle used on a bike from Italy. Is that pretty universal for older road bikes with wing nuts or did some have metric axles with wing nuts?

There's a very good chance that those are actually 9.5mm x 26 TPI axles. The Italian bicycle industry preferred a hybrid metric-imperial threading standard. Fortunately, the major diameter for a 9.5mm thread is only 0.001" smaller than 3/8", so they are interchangeable. 10mm x 1mm was pretty common for rear axles on French and Japanese hubs.