I'd date it at turn of the 90's I just looks like them. Also that LX groupset and being sold with biopace rings puts it about or before then.
Oranges did not really have 'specs' you could get any frame with any component set you wanted, Shimano LX, DX, XT or Suntour XC Ltd/Comp/Pro.
Since it has Shimano LX on it, and it looks fine, penetrate it then oil it.
Either service the Bottom bracket, though rust will probably have hit it so just put one of the cheap cartridge one in.
Headset, if it's smooth and not rusted grease her up.
There are plenty of 1" stems for sale and may be easier and cheaper then putting that one right
Shifter might work/might not you tell us.