Erl,
It would be very unusual if your LP-08 serial# sufix is l. According to Still (Imperial Lugers) LP-08s were not reported past the e block, and there were no 1918 Lugers reported in the l block.
Take a look at this picture, on the right is an l suffix and on the left is b. They are extremely difficult to tell apart by casual observation, it may take a magnifying glass (I know this for a fact, hereby hangs a tale...for another time).
Regardless of this, 1918 DWM were produced into the s suffix block, so the lapse of inspection cannot be accounted for by proximity to the end of the production run.
--Dwight