I just looked at Donald Ball's excellent and detailed book, _The Genealogy of the Locomobile Steam Carriage, 1899-1904_, available from the Stanley Museum, [
www.stanleymuseum.org] . Neither its photos nor its catalog reproductions show any cars with this transverse & longitudinal half-elliptic front suspension - they are all either a single transverse full-elliptic, or two longitudinal full-elliptics.
In fact, I looked through all of _Oldtime Steam Cars_ (as I'm sure Stuart did), which shows pictures of 85 different makes, as well as Floyd Clymer's _Steam Car Scrapbook_, which shows quite a variety of cars from about 1903-1905 - none showed this suspension.
Several images in Ball's book show passenger boxes in front of the footwell, but none have the shape and proportion of the one on this car. One modern photo shows a car with a steering wheel, but it has a much larger reverse lever. Your car's reverse lever and inside throttle lever position look like those pictured for earlier models. The Locomobile picture in _Oldtime Steam Cars_ is essentially identical to the modern photo - the viewing angle is even the same. Oh, and the car in that photo has hub brakes rather than a differential brake.
The burner pictured in the book, which Ball says was essentially unchanged during Locomobile's production, shows holes of a larger diameter and in a different pattern.
All images in Ball's book, as well as those in _Oldtime Steam Cars_, show the boiler water level gauge near the forward edge of the seat.
Ball shows a Mason engine that he says was only used for the first few cars. It doesn't have the bracing crosspiece below the crankshaft or the heavy mountings for auxiliaries on its frame. By 1900, Locomobile were using an engine of their own development, which went through another 4 design changes. The engine in your photographs more closely resembles the later Locomobile engines, but I can't get enough detail from the pictures in the book to make any conclusion.
One more item of interest is the rear axle housing. In addition to the vertical bow, there is a horizontal bow in front of the axle housing - the axle-end casting has sockets for 3 tubes to accommodate it. This style axle housing doesn't appear in any of the book's images. In addition, the tubing on both front and rear axle housings, and the axle-end castings, just look somehow "huskier" than in the book's illustrations.
Quite an intriguing mystery! Hopefully this vague information will somehow move you ahead a little bit.
Kelly Williams
Mount Joy, PA USA