The 1970 Topps #1 Mets Team card has been around for over 50 years now. Until now, 5 different front/ back combinations have been identified, unknown to collectors of Mets memorabilia, to Weaver and Nolan Ryan collectors, and to the professional grading community. A 6th 1970 Topps #1 Mets Team variant might exist, but as of Feb 2021, random market card sampling hasn't yielded a "white border" front with a Variant 1 (yellow) colored reverse. If there is such a Variant out there, please email me.
To date the "Yokai" variants include: 1) 1970 #1 Mets Team with bright yellow back (V1), 2) 1970 #1 Mets Team with mustard colored back (V2), 3) 1970 Mets Team #1 with black line on right front w/ (V1) reverse, 4) 1970 Mets Team #1 with black line front w/ (V2) reverse and 5) 1970 Mets Team #1 with white line on right front w/ (V2) reverse.
Likewise, (5) variants, similar in nature to the 1970 Topps baseball #1 Mets Team card are known to exist with card #198 "Mets Celebrate". No line, black line, white line fronts exist with (V1) and (V2) back combinations.
Only (2) variants have been discovered for the #1970 Topps baseball #197 " Ryan Saves the Day" card. (V1) and (V2) reverses exist.
Canadian O Pee Chee cards have been shown to have similar Variants with no line, black line, and white line fronts. All reverses on the Canadian OPCs are (V2) mustard color.