What exactly is this Lego train motor? I bought this in the early 90s as a spare, since the type of Lego train was being phased out. Presumably the old 12V system.  The original train was given away but I still have this.  I want to sell it but need to know what it is.  It has the numbers 49 5 on the bottom.
It appears to be Electric, Train Motor 12V Modern.