I don't know exactly when S&W started putting speed loader cut grips on Model 29 but it probably was not 1980. I sold my Model 29-2, 6", s/n N798908, on this Forum some years ago and it had factory checkered Goncalo Alves football cutouts. I had a Factory Letter and this gun shipped the last day of 1980, December 31, 1980. 2 pics below
My other 29-2, is a 6-1/2" serial number N439446, and per Roy it shipped in May 1979 and is equipped with very nice smooth presentation grips with football cutout. I haven't Lettered it yet but believe the grips are original to the gun simply because it came to me with all tools, documents, vapor paper, wooden case (flocking actually intact and pretty good shape). 3 pics below