Great pics, I have that strap too. I never thought much about that strap but I saw a video from the 70s and Alvin Lee had one. And now seeing yours I'm going to start sporting my Fender Strap. Mine came with my American Standard Telecaster, which I never use and should sell.
It looks very cool especially with the color of your P Bass.
By the way, love the blazers and ties look, Smooth!
Blue