Sega Master System / Mark III / Game Gear
SMS Power! 18th Anniversary Competitions are coming! Deadline 27th March - 2 weeks and 6 days from now
90451 = Sony Imagesoft (UPC). 5 = GG, 8 = SMS. Not sure what the difference is between 01 and 06. Next is a region code (0 = US, 1 = EU). The final digit is a sequence number (?).