Sky Marshall, plastic disposable preloaded cylinder

Interesting item coming up for auction. … 5/lid/1821
It features a preloaded disposable plastic cylinder.

I spoke about this at length with someone at Colt long ago. I don’t think the idea got very far, but as I remember it, the projectile was to have been made of something like chalk or plaster of Paris, not plastic. This was from back in the day when many felt that a bullet hole in the fuselage of a pressurized aircraft would result in disaster (remember Goldfinger?), which of course is not true. Does anyone else remember this Sky Marshal revolver project?

Projectile used by Colt was a 18 grs frangible made of 67% “Red-Top” plaster of Paris and 33% water. A 19 grains version made of “Hydrocal” plaster was also tried.