Here are two bullet 1871s showing the difference between a 133 and a what I call "sharp transition mold" 133.4 The 133 is clearly concave and is lacking a 3 on the rear crown while the 133.4 is shorter and straight sided and has a 3 on rear crown.

Colors are 133 solid purple with dark purple swirls in dome and 133.4 is very nice amethyst color