I have a different view of Rock Island, but I don't need to share that here, because your Spencer looks as right as rain.
I think this serial number, although not a hit on the SRS listing, does tell you a great deal - this range of Spencers is one of the exceptions to the usual rule that a miss on the SRS list isn't proof of anything. Do an internet search for Wiley Sword's interesting article on the first two army orders of the Spencer Rifle which is called "those damned Michigan Spencers"
I should note that this site put some *** in that D word in the title of the article, but if you use D***ed in your internet search, I don't think you will find that article so spell it the way Wiley Sword spelled it!