Welcome to N54, Nicki. Those Helmar's are a fun, oddball issue. I collect Charles bender but I have one of his stamps or I'd be making and offer.
FWIW here is an article on them that ran in Sports Collector's Digest in 2007.
https://sportscollectorsdigest.com/a...-helmar-stamps
And I agree with the previous answers, I'd keep the sheet intact without soaking off the stamps.