No clue on the serial number... as far as I have read, here, your gap is pretty damn near perfect and I use Breakfree CLP on the internals....and good gun grease on the trigger parts. Thats about it..shoot well
Per the chart in Ruger & His Guns: A History of the Man, the Company and Their Firearms by R.L. Wilson, it looks like the your SP101 was made around the end of 1992.