Last month I had a rare chance to get my own back on one of these charlatans and was able to use the ISMACS convention to do so.
Advertisements had started appearing in collecting magazines offering a good home in a sewing-machine museum for any pre 1870 machines. These machines could be donated or, in exceptional cases, the museum would provide postage expenses.
Having checked that this was indeed a dealer with no museum other than the top shelf in his shop, we put the plan into action.
I wrote to the museum telling the owner about the ISMACS convention and the 170 collectors from all around the world that would be converging on London. I also told him that we would be hiring four coaches to bring the entire party to visit the museum on a given day.
Panic must have set in for he rang the next day, attempted to brazen it out by saying that decorating work was to start on the very day I had proposed. Otherwise we would have been most welcome.
How lucky, I replied, we've had to bring the convention forward a week. I then asked whether the museum car park could take the four coaches and whether the establishment had a full restaurant or only a snack bar.
I added that I was going to contact the local newspaper and TV as media coverage of such an international group would be valuable publicity for his museum.
The phone went quiet and I imagined him pondering on the thought of 170 visitors in his 20 by 20-foot shop, four coaches, press and TV cameras and hungry collectors demanding to know where the restaurant was.
Minutes went by and then he collapsed completely. Told me he had to invent the museum because business was bad. Told me about his wife and three children. Told me the tax man was on his back. Told me he was sorry and would never do it again. And he hasn't -- so far.
Beware "museum" owners, the ISMACS convention group could visit you.....