As usual, one should never trust what they read on reddit (except on AH, of course!). The theory that these objects were in any way related to brothels, or payment tokens therein, is entirely modern and probably bollocks, pun intended. There is zero ancient evidence that these items were used like casino chips, but this is often repeated, even by prominent modern academics. They are rarely mentioned at all these days in scholarship, and are mostly heard about as high-priced collector items.

The modern term for these objects is spintriae (singular spintria), coined (pun intended) by the Renaissance numismatist Spanheim. He in turn took the vocabulary word from a famous passage of the Roman historian Tacitus (VI, 1): "And now were coined the names, hitherto unknown, of sellarii and spintriae, one drawn from the obscenity of a place, one from the versatility of the pathic". Most of the "authentic" ones have an image on the obverse, and a Roman numeral I-XVI on the reverse. Some are erotic in nature, but there are others which are not related to carnal desires: a portrait of Augustus with radiant crown, for instance, or an image of the goddess Ceres. Some have thought that they might be gaming pieces of some kind, similar to modern playing cards, which have standard markings on one side and a huge variety of images on the other side, including erotic options.

McGinn talks about these spintriae very briefly in Economy of Prostitution in the Roman World, mostly as an aside, but he does point out that the brothel theory is probably nonsense (see ch3 p86 n44, if you need an exact reference). It is hard to find a spot where they are discussed at length—like I said, they are mostly ignored in modern scholarship. I would expect McGinn to be best bet.