In that serial range, I record several K-22 Masterpiece units shipping in September and October 1947.
Curiously, K4564 and K4639 are the only nearby K-38 serial numbers, I've found. Those shipped in February and March 1948, respectively.
Keep in mind that the vast majority of K target guns that shipped in 1947 were K-22 Masterpiece units. Full production of the K-38 didn't begin until May 1948. The first K-38 wasn't even assembled until June 6, 1947.
Since you want a 1948 unit, I suspect you can have one if you buy that one. A letter would tell you for sure but there is a high likelihood of K5050 being from 1948.