From Tasting.com, the Beverage Testing Institute, a spot of info I ran across this morning.
Old Tom Gin is the last remaining example of the original lightly sweetened gins that were so popular in 18th-century England. The name comes from what may be the first example of a beverage vending machine. In the 1700s some pubs in England would have a wooden plaque shaped like a black cat (an "Old Tom") mounted on the outside wall. Thirsty passersby would deposit a penny in the cats mouth and place their lips around a small tube between the cats paws. The bartender inside would then pour a shot of Gin through the tube and into the customers waiting mouth. Until fairly recently limited quantities of Old Tom-style Gin were still being made by a few British distillers, but they were, at best, curiosity items.
Interesting concept for dispensing booze, eh? Hold that tiger!
One can imagine a liesurely mid-morning stumble down Gin Lane, tippling from Old Tom to Old Tom, taking the occasional pause to refresh one's self with a brief nap in the nearest gutter.
The last sentance of the quoted paragraph from Tastings.com implies that Old Tom (the true sweet style of gin popular during the Gin Craze of the mid to late 18th century) is unfortunately no longer commercially produced.
While one may find examples of sweetness in a Dry style, this sweetness is the direct result of the distillation itself (ie. grains) and/or of the botanicals used in distillation. Hollands Gin or Genever, usually the lower strength product of a traditional pot still, would generally be even sweeter than that running from London column stills. Plymouth Gin, of which only one example exists today and is marketed by the same name, represents a territory between the two.
My understanding is that Old Tom was a style adulturated with sweeteners after distillation which would have aptly appealed to the Victorian sweet-tooth of the period. We'd consider it something of a dessert gin by today's comparison. Refined sugar from the British West Indies was reaching England in prodigeous amounts at the time, and the public was quick to fixate upon it (Americans have repeated this cycle nearly three centuries later with the proliferated consumption of high fructose corn syrup).