I know it was made in 1970 and I have read that the Glenfield name indicates it was made for a chain or mass-merchandise store.
"Plumber's Delight," and "Cake Decorator" are two that jumped out at me.1.
The second letter of the date code is as follows: F = 1962 G = 1963 H = 1964 I = 1965 J = 1966 K = 1967 L = 1968 So a date code of "JK" would indicate that rifle was made in October of 1967. Straight stock, 21 ½ inch barrel, 40 ½ inch over-all. If you give us that letter we'll be able to tell you the year it was made. Perhaps there is some obscure marking that is near impossible to find – like markings on Waterford crystal, but I see nothing else.