This apothecary shave mug from Col Conk has a great old-fashioned look to it. It also happens to be designed in a way that makes it incredibly effective from a practical standpoint. Look at the design and you can see it's flared a little bit on the top. That actually helps produce more lather out of your soap. This product is also very flexible and, no matter what size of cake you typically use, you'll find that it'll likely fit just fine.
One of the advantageous things about these particular products is that they're versatile in how they work with other options. Obviously, this works very well for soap, but it also works well for shaving cream. If you have a very high quality brush and you use a well-designed mug with it, you'll generally have solved the vast majority of the problems that people have getting enough lather out of the lubricant they use on their face.
The base of this is 3 ´è_´è__´è_´è____ inches in diameter and the top is 4 ´è_´è__´è_´è____ inches, so there is a distinct difference. It'll go great with any set of accessories, whether they tend toward the traditional or the very modern.
Diameter: Base 3 1/4 inches, Top 4 1/4 inches
Height: 3 1/4 inches