cbr1000, I'll try to offer as much help as I can. Jake has the right of it, though. It's mostly marketing.
Queen is a very old company, and so lines have come and gone and come back again. The Heritage Series was an attempt to remake long gone classics using pictures out of old catalogs as a guide.
I believe Queen City is a throw back to the original name of the business. A queen city is a city that's the largest in it's state or country, but not the capital. For example, in Wisconsin Milwaukee is the largest city but Madison is the capital, so Milwaukee would be our queen city. Titusville must have been the largest city in PA at some point, because it's nickname is Queen City. Queen started out as Queen City Cutlery, but I don't know when they cut that down to just Queen. The current Queen City line uses 1095 steel, is only a couple of classic patterns, and they all share one cover material each year. So, the dealers likely separate them out because the Queen lines will come with D2 steel and a variety of covers whereas the Queen Citys are just the one cover material and 1095. The Queen City lines have some embellishments as well, which I haven't seen on the Queen line. For example, the liners on my Queen City Cattle King have a pattern stamped into them which is very nice. However, they share patterns with the Queen line, so this year I was able to pick up a Queen City 49 and Queen 49 that are identical with the exceptions of cover material and steel.
From what I've been able to tell, the Keystone line is S&M's standard line. The F&W line is their premium line. The F&W typically have a higher grade steel, like ATS-34, whereas the Keystone line uses 420HC. This is not a hard and fast rule, as many of the short runs that Queen has been putting out have used the keystone shield and use all different types of steels. I currently have a mini-trapper in my pocket that was made for their Historical Society Gathering this year that sports the keystone shield and 1095 steel. I also know that they've put out F&W knives with D2 steel. In fact, there's at least one run that I know of that had ATS-34 offered with one cover material and D2 with a different cover material and both were marked F&W.
Basically, the Queen lines are going to be a bit more confusing because the company is so old and has switched hands multiple times. Each owner brings their own marketing strategies with them, and tries to pay homage to the company's history in their own way. For the current production knives my strategy is to look at their website. If it's Queen City it's 1095 steel, satin finished, and fancy shields. The Queen line is D2, polished blades (as well as they can polish D2), and plain Queen circular shields. The Keystone line is 420HC, polished blades, and the keystone shield. The F&W line is ATS-34, polished blades, embellished bolsters, and fancy shields.
If the knife isn't on their site it's a short run and all bets are off. You have to take those on a knife by knife basis. It seems that they make the knife they want and then try to fit it into a line that most closely matches it, instead of building the knife based on the criteria of that particular line.
I agree with you that it's difficult to decipher without seeing them in person. I didn't get into Queens until I started going to local knife shows, and they have a table at every show in Wisconsin. If you prefer a simpler method of categorizing Case or GEC are safer bets. At least until you watch the videos that Jake suggested and become proficient at spotting the differences by looking at pictures.
Just because I'm a good feller.
