Texgun...
Sounds like you might have a later model "R" with a semi-beavertail forearm with a blunt tip and checkered side panels. The Model Rs were made from 1932-1960.
Your serial number puts the date of manufacturer in either 1952 or 1953. However, the surest method of identifying the year of manufacture is by correctly identifying the Lever Boss Code.
The Lever Boss Code "letter" should be inside an small OVAL together with one or two inspector's numbers in front of the Lever Boss Code's letter on the front side of the lever boss. If it is, in fact, a letter "E", then 1953 is the year your rifle was made. Unfortunately, this "Code" letter was stamped very light... and it may not be possible to read.
There are a few other ways you might identify the Model "R". The R-model had a larger stock than other Model 99's, heavier through the comb. Measure the checkering on the rifle's forearm, a Model R's checkering was 10-5/8ths inches long and only the forearm's side panels are checkered.
As to why most people write only the first three or four numbers of their rifle's serial number, I have no idea. I always assumed it was because they didn't wish to give the rifle's full serial number because someone might claim the rifle was their's... and they'd have the full serial number to PROVE it!
However, with only about HALF of the rifle's serial number, claiming ownership would be pretty hard to do.
Other than that, your guess is as good as mine.
Strength & Honor...
Ron T.