AC 428: were any roadsters all alloy?

A few years back, when I was at the Queen's English show in Van Nuys a bloke shows up in a right drive roadster and says it was the only all alloy one. Was I being played?

Also I read there were three prototypes, one with hidden headlights, one a four door (l'd love to see a picture of that). Don't know what the third one was but maybe that was the one with the odd experimental engine, the head engineer's pet project. That one wasn't called the AC428.