The 350 was introduced in 1952 to replace the model 615. Approximately 6100 were manufactured between 1952 - 1960. The 234500 serial number represents 1954 production. Like the 615 the letter designation following model will refer to engraving. 350AS demotes A engraving while 350CS notes the C grade engraving. There are a pair of web sites that will give you all the proof marks right down to the individual fitter and finisher. By the way the bores on my 615AS are just as tight measuring .718 & .717.
