Since this subject isn't covered very well, I thought I'd make a decent guide on identifying the different types of Genesis reprint cartridges. As far as I have seen, there's only two companies that produced reprints for Sega as well as third-party companies: Accolade/Ballistic and Majesco.
How do you tell which type of reprint is yours? Just examine the following elements:
If you flip over the paperboard box and examine the fine print at the bottom, you should find Majesco's address as well as "Assembled in Mexico" written somewhere nearby.
Accolade/Ballistic reprints will usually come in the standard plastic clamshell box with a sticker on the back that reads "Published by Ballistic" and a mentioning of "Assembled in Mexico" somewhere near the fine print. Some games may also include a then up to date ratings marker from the ESRB that wasn't there on the game's original printing.
On the back of a Majesco game cartridge, you will find a large black sticker that thoroughly covers an Acclaim Entertainment logo. This sticker will be larger and darker than those used by Accolade/Ballistic.
As mentioned above, Accolade/Ballistic used smaller stickers to mask the Acclaim Entertainment logo on the back of each cart. Even when placed crookedly, the stickers still stay within the bounds of the logo outline. It also appears that some cartridge molds were doctored to print the Sega logo instead and it probably saved some money on stickers in the process!
The ROM Chip:
All reprint carts use security Torx screws, so opening them shouldn't be difficult since most hardware stores sell the appropriate bit. Once you open the game cartridge, you will not only know the manufacturer, but the manufacturing date as well. Most ROM chips will come with a four digit date code: the last two digits of the year, followed by the week of production. Looking at the ROM chips above, Majesco's "J9810" means the PCB was manufactured on the tenth week of 1998, while Accolade's "9633" means the PCB was manufactured on the thirty third week of 1996.
If you examine the game's PCB and notice that the connector is missing pins, it is because the pins that originally occupied the space served no purpose to begin with and were simply removed as a cost saving measure. Function and gameplay will be no different between a reprint and an original cartridge of the same game.
The Owner's Manual:
When examining a Majesco manual, you should notice two things:
1.) It's entirely printed in black & white.
2.) On the warranty page, Majesco will be mentioned instead of the game's original publisher.
Accolade/Ballistic reprint manuals will be slightly different:
1.) It will be either entirely black & white or black & white pages with a cover printed in color.
2.) On the warranty page, the game's original publisher will be mentioned with no reference to Accolade/Ballistic.
Thank you for taking the time to read my handy guide. If you have any corrections, compliments, complaints, or general comments, just fire away!