Found this Tiny Cartridge (which is quickly becoming one of my favorite gaming sites). It's a calculator hidden in a Famicom cart shell.
http://tinycartridge.com/post/142304073/the-original-mario-calculator-handheld-no-mario (http://tinycartridge.com/post/142304073/the-original-mario-calculator-handheld-no-mario)
Those are nice, but unfortunately the size is bigger than a real cart.
What year were they manufactured?
I'm not sure, but they are around for quite some time (several years) now.
They came out as prizes in the UFO Crane Catcher games in Japan about 3 years ago, so I'd say 2006. Of the top of my head they have three version; SMB, Zelda, and Ice Climber.