Actually, many Grados had a G on the front, that was their logo. What distinguishes the cartridge generations was the color of the plastic body and its shape. IIRC here would be a kinda time line:
older - Grey = F series, Black = G series, Beige = M series, > newer (please correct if my recollection isn't accurate)
some of the cartridges had the Model letters molded into the front as well so that could give you some idea of the model or line type.
This is their replacement stylus history. The different stylii are distinguised in series by the plastic color of the canteliver carrier and the color of paint applied to the plastic dots on either side of the carrier.
http://www.gradolabs.com/frameset_cart/stylus_hist.htm
Replacement Stylus History
FTR = GTR = NO LONGER AVAILABLE
FCR = GCR = NO LONGER AVAILABLE
FTE = GTE = NO LONGER AVAILABLE
FCE = GCE = NO LONGER AVAILABLE
FTE+1 = GTE+1 = MTE+1 = XTE+1 = ZTE+1 = BLACK
FCE+1 = GCE+1 = MCE+1 = XCE+1 = ZCE+1 = GREEN
F3E+ = GF3E+ = MF3E+ = XF3E+ = ZF3E+ = BLUE
F2+ = GF2+ = MF2+ = XF2+ = ZF2+ = RED
F1+ = GF1+ = MF1+ = XF1+ = ZF1+ = SILVER
N/A = G+ = M+ = X+ = Z+ = SILVER
N/A = G1+ = M1+ = X1+ = Z1+ = GOLD
N/A = G2+ = M2+ = X2+ = Z2+ = GOLD
Other option for discovering the type is to check the various Ebay auctions and see which one lines up color, appearance and stylus color dots.
Good luck and maybe post a photo or two.
Regards,
bart
