First of all the S&W factory never "Chromed plated" at the factory. Nickel Plate yes.
The R serial number began in 1969 according to the SCSW. R001-R30000 were manufactured in 1969. Model 33-1 .38 S&W Ctg?
A few pictures might help you get more information
I'm a S&W collector but not a mind reader