Hi Gayanth,What a nice stamp blog you have here! I’ve never been to Croatia, so it sure is great learning about the country through their stamps. I am more interested in animal stamps, so I looked into an online stamp catalogue I usually visit and found that the frog here in the letter was issued on April 8, 2013. It’s a Fire-bellied toad (Bombina bombina) . As for the set of 4 stamps, it was issued in February 21, 2014 with the title Children’s World Pets (Chincilla, Rabbit, Guinea Pig and Hamster).