shnibop,
I have a very similar AVA stem that NLerner traded me. He told me it was not a "death stem". I trust him. The clamp bolt design is just like the one to which you linked. I did not measure that stem's clamp area, but it has a Japanese randonneur bar in it as we speak. I can only assume that that bar has a 25.4mm diameter. I have seen more modern French stems with 25.4mm clamps and, of course, Cinelli sold stems with 22.0 diameters that accepted a 26.4mm handlebar.