Original Railmaster 2777-2 circa 1955. Issued with special Caliber 283 with Swan Neck Regulator .
Perhaps 20 were produced for the Canadian market. The movement was never used again.
They were so obscure that Omega, circa 2000, had no idea these Railmasters, or the movement, ever existed.
It took many years of research by @Bill Sohne to solve the mystery. https://www.watchprosite.com/page-wf.forumpost/fi-677/ti-401501/pi-2398426/
Platinum anniversary Speedmaster was made in a total of 69 pieces. I don't know if it was the lowest but it's got to be close. It's incredible in the metal!