I've had two, still have one. They were not just available with stock purchases. I think these are the only Marlin pump that you will find marked two different ways on the tang - N° 47 or MOD. 47. Early Marlin pumps were only stamped using the N°. The 37 & 38 were only stamped as MOD., as far as I know, not sure of the Model 32. The early catalogs listed them as 'Model No. xx'.
The 1929 fall Sears catalog lists it as "new" and 1929 was about the last year Marlin made pumps, it also was the start of the depression which would have hurt sales. It would be interesting to know the years they were offered with stock purchases.