I used to collect antique still banks. Yours is listed in in Moore's "The Penny Bank Book". It lists it as an Elf, and the design was originally cast as a door stop, but the factory later changed the mold to include the coin slot so as to produce it as a bank. It is known as a 'factory conversion'. The book lists it's scarcity rating as 'C' which is "getting hard to find". It does not date it, but I would imagine it is late 1930's. very cool find. too bad it wasn't full of coins.