Storybook (Nursery Rhyme) Mugs, Imperial
Imperial certainly got its mileage out of this mold. Originally made in Helios green from 1967 to 1970, red (Sunset Ruby) from 1968 to 1973 ("EWR" on base, limited edition of 390), cobalt (Aurora Jewels) from 1970 to 1972, amber from 1973 to 1975, Horizon Blue from 1979 to 1980, and Meadow Green from 1980 to 1981. They also made an experimental vaseline. Some of the amber mugs have the words "EWR Nixon/Agnew" on the base, apparently to commemorate the Richard Nixon and Spiro Agnew political campaign. "EWR" stands for E. Ward Russel, who had these made.

Amber, 15-25
Amber, Nixon/Agnew, 30-45
Blue (most common), 20, 25 (both 2004), 14 (2008), 15 (2012)
Horizon Blue, 15-25
Meadow Green, 33 (1999)
Meadow Green, 16 (eBay 2003)
Red, 55-80