What Is It?

Almost looks like it could have been a handle on a disconnect box of some type?

Or maybe a tool that is used to open a tamper-resistant door on an electrical panel?

It could be a throttle or choke lever or gear shift off a piece of equipment...looks like a pivoting handle of some sort...

What is the approximate size?

It looks like 1/2" wide maybe 1-1/2" long?

Cutting height adjustment lever for a lawn mower?

It's about 2" long, thin metal...like those cheap shim keys for specialized enclosures, but not sure which specific application.

Looks to me like a "wedge key shim", used for aligning steel plates prior to welding, in tank and ship construction.

Take a look at the video here:

http://www.fitupgear.com/fitupgear-products/fitupgear-wedge-key-shim/
Mark

It's a whimblemajingale to wind up the moon...or so my father would tell me...lol

Skeleton key for a UFO?

It'd be comforting to know that they need master keys too.

Janitor's key to access soap or paper towel dispenser?

It would be a good guess, though not technical.

I am hoping to get an actual, but not expectant.

It looks like part of a disconnect switch to prevent opening the door when the switch is in the on position.

It can be bypassed by pressing it inward with a screwdriver,while applying downward pressure on the handle.

Used by maintenance people to check fuses with power on the circuit.

Most likely:

It could also be part of a lockout device.Slip over the device,pull to bottom of slot,and apply lock.;For instance, a circuit breaker lockout.

Okay, the guys over at ElectricianTalk.com solved it: Locking tongs release

"Size is not important." _{- Anon}

_{Except it is important if one wants one's wallpaper to stay on the wall...}