1880? 2 cards from the green set by Wemple and Kronheim, stamped "Reward of Merit."
These cards of "The Two Dogs" and "The Dog and His Master's Dinner" include a prose text of the fable on the back side. I believe that the two cards did not come from the same printing, since they use different typeface for "Reward of Merit" and since their ink's hue tends to green and to blue, respectively.
1880? 2 more cards from the green set by Wemple and Kronheim, stamped "Reward of Merit" and then stamped again by Robinson Brothers' Picture Frames of Springfield, MA.
These cards of "The Eagle, the Lamb, and the Crow" and "The Heron" again include a prose text of the fable on the back side. Both the physical overstamping and the double function (reward of merit and advertisement) seem gauche to me.
1880? 1 TH card from the above set by Wemple and Kronheim, stamped "Reward of Merit."
This card, like the two above, includes a prose text of the fable on the back side. The color printing here may be among the best for Wemple and Kronheim cards. Here, as there, "Reward of Merit" tends to have some filigree work around it. It has the fancy "R" found in the card depicting "The Dog and His Master's Dinner."