Some friends were discussing the custom of ordering whiskey or some other spirit with a "beer back," and that got us talking about that and the related bar calls, like "shot and a beer" and "boilermaker." (Not to be confused with the Purdue University campus icon.)
Shot and a beer is traditionally the working man's drink, in part due to economics. It would have been considered a trade-up from just drinking beer. It also ties in with the idea of session drinking, which is something people talk about in Great Britain more than here. Session just means you are going into an evening of drinking with a modicum of a plan, based on how much you can afford to spend, what you like, and perhaps also a calculation of how drunk you dare get and when you want that state to be achieved. The shots can be any spirit, and often among some of my younger friends it is tequila, vodka, rum or Jagermeister rather than whiskey.
"Shot and a beer" as a bar call also means you're asking for well whiskey and the house's cheapest draft beer. The "beer back" call usually follows a specific spirit call, but the orderer is still indifferent about the beer. If you are calling the beer too, you usually don't use the "beer back" terminology, you just place the two orders.
I haven't heard the boilermaker ordered as such very often. Although Wikipedia disagrees, I would say the term "boilermaker" means the spirit will be whiskey. Here again, we're talking well whiskey and draft beer. It's also not uncommon for the beer to be a pony, i.e., a smaller glass, often called, quite literally, small beer.
Again, working man's drink in working men's bars. Part of the idea was that the boilermaker would be the house special, a fixed price, and usually the cheapest way to drink at that establishment, save for quaffing the house draft all night. I've never known it to be served with the shot in the beer glass and never knew many people who liked to drink it that way. The shot in the beer I've also heard called a depth charge and now, commonly, a ______-bomb, e.g., Jager Bomb.
Again, in the tradition of working men's bars, if you were drinking straight whiskey, period, you were probably looking to get plastered as quickly as possible and wanted to be left alone. The shot-and-a-beer call was an indicator of sociability.
Personally, I might get a beer back when I feel like a whiskey but I'm also thirsty, though I probably get water back most of the time. Sometimes, though, there's nothing quite so refreshing as chasing a good whiskey with a cold lager.
In a working men's bar, whiskey rocks, whiskey and water, whiskey and soda, etc., would have been considered effete or pretentious, that being the way whiskey was taken among the middle and upper classes, the middle class being nothing but a bunch of aspiring snobs anyway.
A little bit higher class call for the exact same thing is to order a whiskey with a beer chaser. You just don't hear that word--"chaser"--much these days, though it was common in my youth. I can recall bars where the beer chaser was assumed, and provided at no additional cost, so you had to speak up if you did not want it.
What whiskey? It would depend on where you were drinking. Certainly in the South it would be bourbon. Pre-prohibition it would have been rye in a lot of places. In the Northeast it might be blended whiskey or even scotch or Irish. In the midwest it might be Canadian.
It's never been wrong to ask the bartender to show you what's in the well, within reason of course.
How the shot/beer combo picked up the name "boilermaker" is unclear. My theory is that boilermakers, as skilled craftsmen, would have been the highest paid workers patronizing a particular bar, and may have been the only ones who could regularly afford to alternate whiskey with beer throughout the evening. If you ordered a whiskey and a beer you were "drinking like a boilermaker," and eventually that became the bar call.