The LERK K-38s known to me are K4563, K4564, K4593, K4709 and K23280. Until that last one turned up, I had suspected that all LERK K-38s would be found with serial numbers below K5000 and almost all between K4500 and K4850; we know from records that the first production order for K-38 Masterpieces was for 350 units, but we don't know their serial numbers. K4500-K4850 is just a guess on my part. Not all of these guns will be LERK specimens. Some K-38s are known from this range that have knobless ejector rods.
There are possibly some salesman samples in existence with SNs below K2500, and they may be LERK guns. There may be a few other LERK guns in the K22xxx or K23xxx range that exist only because a few more prewar parts were found in storage.
It sounds like a big jump between K4500 and K22xxx, but it's not. K-38s in the higher range were being shipped only a couple of months after the known K+four digit guns were released into the wild.