According to the Scamp site, early trailers all had a serial number starting with an "E". Adding the above note on dates, it looks like:
Top line: 5 81. Your Scamp was built in May of 1981
(They tried to stamp an "8" but didn't hit it straight, making it a partial number looking like a 3, but it doesn't look like the "3" in the lower number at all)
Bottom Line: Serial number is E 1 10344
I am guessing that E= company identifier, the first 1 = 1981, and the 10344 = the production sequence number.
Although Scamp should have changed over to the standardized 17 digit VIN
by May of 1981, it's entirely possible that they didn't, the mail is a bit slow getting to where they are at!!!!!
Try phoning Scamp and asking them if this makes sense.