Tricuni No. 6

You might have guessed it NLN, I had a pair of those boots. The outer nails in the picture are Tricuni No. 6 and the stud type nails that would be in the sole and heel, Tricuni No. 1. They gave a good grip on wet rock but, as you might imagine, they were ridiculously heavy. Vibram soles put an end to nailed boots.