The Van Depoele Incandescent Lamp
It was announced in the Western Electrician in March of 18881 that the Thomson-Houston Company purchased the motor business of the Van Depoele Electric Manufacturing Company of Chicago. The Van Depoele concern thereafter was to devote its efforts to the production of arc and incandescent lighting. In December of 1888 an article appeared2 that described their new incandescent system.

Their lamp is shown to the left. They said:

"The lamps are manufactured in sizes from 10 to 150 candle power. The socket is constructed with the utmost simplicity. Two kinds are used, the plain or keyless sockets. The key-sockets may be turned in either direction, and it is impossible to injure them by turning. The lamp when in position is held firmly in place, and cannot possibly jar or work loose."
An average life of 2000 hours was claimed. No mention was made in the article about the design of the lamp base.

In the July 13, 1889 issue of the Western Electrician it was announced that the Thomson-Houston Company purchased the lighting business of the Van Depoele Company2. Thus, Thomson-Houston had purchased the entire businesses of the Van Depoele Company.

It's of interest to mention that, to the writers knowledge, the William J. Hammer Historical Collection of Incandescent Lamps never contained a Van Depoele lamp.

References
1) "Purchase of the Van Depoele Motor Business by the Thomson-Houston Co.," Western Electrician, Vol 2, No 12, Mar 24, 1888, pg 145.
2) "Van Depoele Incandescent System", Western Electrician, Vol 3, No 26, Dec 29, 1888, pg 328.
3) "Van Depoele Company's Business Purchased", Western Electrician, Vol 5, July 13, 1889, pg 16.