This is puzzling. K2289xx should be from 1955, long before model numbers were even established, let alone applied to individual revolvers. This should be a .22 Combat Masterpiece, but not a Model 18.
On the K target guns, model numbers didn't show up until about serial numbers in the K326000 to K330000 range, depending on the model, with a few Combat Magnums actually being marked Model 19 a bit earlier, in the K316000 to K317000 range.
The lowest number on a .22 Combat Masterpiece Model 18 that I've discovered is K334471. K334814 is a Model 18 that shipped in November, 1958.