The term "soap bar" refers to a particular pickup housing geometry that is derived from the appearance of the Gibson P-90. (And it has nothing to do with configuration of the coils inside.) A notable feature of all soap bar shapes (There are many.) is direct-to-wood mounting. This pickup has a trapeze style mount, and a shape very similar to a standard guitar humbucker, rather than a soap bar.
Because of the resemblance to a guitar humbucker, it is very likely that it is a humbucking pickup. I can't imagine that there would only be a single coil inside, but it is possible, nonetheless. If you want to be certain, there are two ways to check. Firstly, look at the underside of the pickup. You may be able to see the coil(s). If you cannot see them because of epoxy potting, then wire the pickup up and have a listen. If there is no 60Hz hum, it is a dual or quad-coil pickup. (Humbucking.) If there is 60Hz hum, it is a single coil or a tri-coil. (Not humbucking.)
Another option that may be useful to you is to purchase magnetic viewing film, and lay it over the pickup. Magnetic viewing film will not allow you to determine if there are stacked coils, but it will show you how many coils are right under the strings, and give you a picture of the shape of the magnetic field and pole piece configuration.