These are not listed in the Scott standard catalog (NOT Scott #68) but are listed in the Scott Classic Specialized catalog as OL1 and OL2, local official stamps.
For a brief period of time (Nov. 7-25) after independence in 1918, the Boy Scouts were used to deliver mail in Prague. This is a highly collectible, specialized area in Czech philately.
See YouTube video from Society for Czechoslovak Philately webpage/CCNY.
https://youtube.com/watch?v=uBz0ZX3xoTE