Hi I have an A 5564 with a Z above ,in .177. this has pins instead of screws for the trigger and Sears..straight scope ramp...it's in a first model stock no 2*** ,
I remember reading in a earlier post they did two runs of A prefix late sixties then early seventies ..and not sure but the seventies where all in 22
Hopefully someone with a lot more knowledge will be along soon
Cheers ian