It looks to me that you have a Singer 201, not the 99.
AE- 675491 685490 201 10000 September 22 1937
This site says that the 201k was "undoubtedly the pinnacle of Singer's quality machines."
http://www.sewalot.com/singer%20thro...the%20ages.htm
Congratulations on getting that machine - and now be advised that you have just been bitten by the antique sewing machine bug. You will find yourself watching garage sales, searching craigslist, looking everywhere for another old machine that needs a good home. I know, because it's happening to me too.