A very nice little .22, one of my all time favorites, got my first one new in the 1960s.Importation into the US stopped in 1968. The frame is aluminum.
They are uncommon here. Many books call them a variation of the more-common "F" series, but they are not.
They should be kept well-lubricated.
I don't have any reference handy to see when production started, but I would think after 1958.