To shed a little more light on the differences in the shape of various lasts, I have compiled an image of the Barrie, Trubalance, and Modified lasts from the Shoemart website. These lasts are known to be more roomy than some of the other Alden lasts and I think this overhead shot gives you an idea of the differences in shape.
There is much discussion to be found on the various shoe forums about sizing and fit and there are many opinions. My experience with my own shoes and my professional experience with sizing people in the Barrie and Trubalance lasts is that they fit about a half size larger than what they think their shoe size is. Someone comes up to me and says “I wear a 9” and there is a good chance that they will be comfortable in an 8 1/2. This is just what seems to be common for most people.
There is no perfect formula for figuring out what size shoe you need without trying it on. I would not recommend buying an expensive pair of Aldens without having ever tried them on unless you don’t mind sending them back. That said, with some research on the shoe forums and asking around, you can probably make a decent guess. I am always reluctant to tell someone what size shoe to get if they haven’t tried it on.
My sizing info: I wear 9E in Barrie and Trubalance. I wear the E (wide) fitting because I have a high instep. My foot is tall – not so much wide. I tried on a pair of Alden plain toe boots on the Modified last and a 9 1/2D fit me perfectly. In many sneakers I wear a 10D. I have a pair of Johnston & Murphy suede wingtips in 9 1/2D. I had an old pair of Florsheim longwings in 9 1/2D.
I do not know if the shoes in the photo are all the same size. The plain toe shoe shows size 8D in one picture and I would assume the others are close to that size but am not certain. Also the different welts give the look of different widths, especially from the bottom, so keep that in mind.