Odd Little Sign

After driving for hours in North Dakota with little success in finding mathematically significant roadsigns Jamie stumbled upon these little signs along the side of the road. They are placed by the highway department, but they appear to be house numbers. While cruising down US-2, after figuring these signs out, it was a fun find! These Little White Sign are an interesting genre of Road Sign Math.



Solution
The math here is easily overlooked due to the size difference in the numbers, but a little quick subtraction and you realize it's essentially a 4, 2 sign.

$$\sqrt{1,659 - 1,655} = 2$$

Background
This sign is found on US-2 heading east towards Grand Forks.