RP-
Well, we have a hit on that serial number, congrats!
115720 - 98R - 99 - CO M 1ST TERR USV INF -
That Model 1898 rifle was issued to Company M, 1ST TERR USV INF in 1899. The stock cartouche indicates that it was completed in 1898.
This rifle would originally have had a Model 1896 rear sight. It was later reworked with the Model 1901 rear sight. This modification was quite common.
You can get some documentation (for a fee) from Springfield Research Service at
(You need to Login to view media files and links)I don't know if I would recommend 'restoring' as it is in good order as-is. The rifle looks complete, but has a little wear and tear over the last century. It could use disassembly and a tender cleaning.
$600 would be a fair price, slightly more if the bore is very good.
Ken