Not a very popular thematic,except for numerous Asian New Year issues, like this one: issued Oct.31st,1970
Stamps of wild boars are more common. The upper one,issued 1909 (catalogues give no exact date) probably is the oldest stamp showing a member of the swine-family.In German it is named "Pustel-Schwein". Several "blues" exist and different perforations and overprints. The lower stamp is from the Red Cross-charity set,issued 1918.
Some New Zealand pigs, Year of the Pig 2007, and a whimsical one from Canada, 2019 - happy little piggies ,,,