Not usually, but maybe I guess. Normally it's for illustrative purposes in a catalogue or an article, and yes, you can see the wax in the pictures. For an example of this, Nicholas(?) posted a Chas.1 halfcrown with a superb provenance going back nearly 200 years where you can see the wax on the image in Hamilton-Smith's 1919 sale. I can't remember which thread, but it's probably Coin acquisition etc. However, museums also took a wax impression on occasion, if they wanted a record of the dies. e.g. My Edward the Elder penny is unique, so when Lockett bought it at the Vatican Hoard sale, the BM took an impression which left a tiny blob of wax.