Now I have found it (under the name Senkesin) in an Indonesian newspaper from the 1950s called Waspada. I don’t know Indonesian, but the images in this advertisement are the clearest that I have found for this product.
If someone would like to read what it says and tell me the gist of it, that would be wonderful.
What is great about this add is that we can finally get a good view of the monkeys. The Thai advertisement from the 1930s which I read said that the main ingredient in Sinkesin came from the sex glands of langurs. The two cute guys in the picture here, however, look like chimpanzees.
In any case, it is great to finally see the Latin term for this secret medicinal ingredient – Masculinum!