Yeah, I assume L-D changes followed I-J's, so that's definitely much later than 1910. Around 1913, the crank nut switched to the non drive side and the serial didn't move to the seat tube until later (~1915?, I'm not sure). My Iver is 195xxx and is about 1912. Don't know if the L-D had their own serial numbers or were sequenced within the same line as the I-J, but even in the former case, I doubt they would have built well more than double the number of L-Ds.
You sound a little discouraged by the later year, but don't be (unless you paid more based on it being earlier)—that's going to make a beautiful bike and these ride really nice. Great find, especially being the tall frame!
As for parts, a standard 1" threaded stem fits my Iver and some of the Brooks saddles were contemporary to the bike, so you can build a rider pretty affordably as you hunt for the original parts. Front hub is a probably a 90mm, which will be a little annoying as 100 has been the standard for so long, but you can likely find a New Departure Model W for real cheap on ebay (I got a pair in good condition for $20) to get you going.