(click on pictures to enlarge)
Stewart pencils were cheaply made and had lighters built into the top. Some, as the example shown on the left, were advertising pieces. All are marked "Pat Pend. USA" on the clip.
The design is practically indistinguishable from that patented by William P. Aron as number 1,750,255 on March 11, 1930 (view here), but these are significantly newer, dating to the late 1940s or 1950s.
Note that there are two styles of the caps. The one on the right is more difficult to find.