Japanese Whistling Tea Set 1960's

Back in the 60's when my brother was in the Navy, he visitied Japan and sent this tea set to our Mom. The set is 15 pieces, pot, creamer, sugar bowl, 6 cups and 6 saucers. He told her the set whistled when hot water was added. I can't verify this because the set was never used. He displayed it in a cabinet. When she died 7 years ago, the set was packed away. Set is "cracked" green with gold accents. One side of the pot has a horse?, and the same design is on the inside bottom of each cup. Opposite the horse on the pot is another design. I have no clue what it is. The saucers have both the horse and other design on them. The bottoms of everything are stamped Made in Japan, and what appears to be Japanese writing. I have more pictures available, via email. Can someone provide any information at all on this tea set, age, value, history, etc? Any information would be greatly appreciated.