This series is small – only two sets with one rare variant. These sets belong together because they are both water related, identical sized stackers, with same pour hole pattern, and same markings.
Both sets stand about 5” in height. They have a 4-3 pour hole pattern and cork stoppers. Both sets are stamped “Japan”. Interestingly, both sets appear to craze easily.
(Reference: 1001 Salt and Pepper Shakers
by Larry Carey and Sylvia Tompkins, page 111)
An unusual, slightly naughty, variant of the mermaid stacker has been found and is pictured below.