It doesn't mean that the shares are (were) bogus, just possibly worthless, dependant on when they were bought and sold. The 19th century scams were rather like a pyramid sell, if you purchased shares at company formation and knew when to sell, (insider information) you could clean up. It was the poor dupes who bought in on the basis of outrageous promotional reports.
Often, the ‘consultants’ would basically be playing whatever tunes the people paying them wanted, typical were the Francis family, Matthew and Absalom being possibly the worse. Sometimes, the reports would be written by people directly employed by the fraudulent company. For example, Thomas Glanville was a Cornishman who moved to Wales as an opportunist when Mathew Francis died in 1869. He was a captain at the Pen’Allt mine near Nantlle Vale, which was an outright fraud, and later captain at one of Fells companies formed to work the Talybont mine. Here at one point he reported on an entirely fictitious new lode on land where the company did not even have mineral rights, it was on dead rent for operating the dressing floors.
At that time, the directors of the company, which included Fell and his associates R B Fastnedge and Edward Hilton, (also Cambrian directors) decided to increase the share capital accompanied by outrageous reports from Glanville and even letters from possibly fictitious authors in the Mining Journal.
So here, we have a situation whereby the share value would peak, and anyone who was on the inside of the fraud, would know that this was the time to sell.
My avatar is a poor likeness.