Missing tang stamps are always awesome, due to being uncommon.
I just bought a Victorinox Grand Prix. The main blade only has a tang stamp on one side.
I think I have the same model, no tang stamp on the back, modern, post-73 small blade, square phillips with can key, tapered reamer, pre-78 aluminum head tweezers. Unfortunately I found it without the original automobile scales, but with some restoration and new silvertech scalest it turned out nicely anyway.