okfive-o's post is interesting. If correct then this one would be from the original production run of 2,600 units in 1964. It letters as shipped in April of 1968. Apparently these were slow sellers from the start. Went to a store in Florida and it was acquired last year from a Florida seller in a Gunbroker sale. Don't recall the city but looks like it didn't go far in 53 years.
old bear, they did indeed come in nickel.
S259872 shipped 4/22/68 Jesse Harp, Co. Tampa FL
Sorry for the horrible photo. It looks much better in person.