Reving High & Governor Spring

I haven't used my lawn mower for years. Did some work on it and finally got it to start again. However, it was running way too fast. Looking at the governor spring, I realize it only had one spring. The motors I have seen so far always had two. However, I didn't really see where the second spring could hook on to and how could a spring get lost anyways. So does my 1995 Briggs and Stratton HD3520A only have one spring? Everything seems to move pretty freely so I don't think it's running fast because something is stuck. PS: I tried to find the engine model number and checked all three proposed locations but couldn't find it. Either it rusted away or they didn't print engine models back in 1995.

For an almost-old timer such as myself "way back" in 1995 is essentially modern times. Anyway to what extent this will help I don't know but I encountered the same issue and the part # was on a bracket which
was at that point in time in the container of the parts I had removed to do the repair. Seems was near the air intake, on a bracket. And the number was somewhat faint. If I remember right seems it helped to hold near bright light.

A picture of the carb might really help more than the engine numbers in this case. With the air vane type governor a single spring might be correct, the throttle adjustment pulls the spring and the AV governor pushes against it.

Thanks for the responses. Attached is an image. It looks pretty dirty but it's actually moving pretty freely. If this one indeed just uses one spring could it be that the throttle valve somehow disengaged and is always open? Seems unlikely, though. Now my air filter is pretty bad. Could it be that this is a problem? Then again, if not enough air can come in then the motor should choke, not running really fast.

if moving the air vane further away from the flywheel does not close down the throttle then the carb has internal problems.
The plate on the throttle shaft can come loose, it is only held in with a barb.
A single spring could be correct on your engine and the springs make the engine go faster not slower