First off, I live in the USA. I know that Lawnmower man for the gameboy was only released in JP and EU. I have been given a prototype version of the Lawnmower man. 

Here's the pic:  http://i.imgur.com/uzHWWJj.jpg...

What do you guys think? What am I looking at here? Is it the EU prototype or is it a prototype of an unreleased NA version? How would I be able to tell. I have booted the game up and it works. Also, sorry for the potato quality photo.

The other is primal rage. Thought I should probably mention that.

It's probably just the euro version put on a cart for review/interest to see if they should release it in the states.

Your best bet would be to dump it and compare the code with the ROM of the retail release. If Lawnmower Man were a proto of an unreleased US version, I guess you could see if the game has company/copyright data for a US distributor or something.

Oh, what is the year on the label? Can't make out the last digit. If it is after 1993, then it is possibly either a prototype of an unreleased US version or an interest check cart like Adler said.

It's hard to tell but it appears to say 1994. When loaded, the game says 1993 on the start screen. But the label is 1994.