Felsenthal Graphical Site Table

This one-sided wooden instrument, similar to a slide rule, was designed in 1964 by Felsenthal Instrument Company but, according to the accession file, made at the Fort Sill Bookstore in Oklahoma. It was used to position a 155 mm howitzer armed with high-explosive M107 shells. The indicator is clear plastic with wooden edges held together with brass screws.
The bottom of the base has a scale labeled Site and Vertical Interval. The lower right corner of the base is marked: Rule 2 (/) Apr 64. On one side, the slide has a scale for range and scales for the Target Above Gun (TAG) and Target Below Gun (TBG) with charges of 5 or 6. The other side of the slide has another scale for range and TAG/TBG scales for charges of 3, 4, and 7. Tables for the observer's position are on the left and right ends of the slide on both sides. Both sides are marked: HOW 155 mm (/) FT 155-AH-1 (/) PROJ, HE, M107 Rule 2 (/) Apr 64.
Tables for angling guns to the left and right at various distances are printed under the slide. The back of the instrument has instructions and examples of use. The markings suggest that this rule was distributed in a white bag. Compare to 1977.1141.26, which may be an earlier version of the instrument.
Currently not on view
Object Name
slide rule
date made
Felsenthal Instrument Co.
Physical Description
wood (overall material)
plastic (cursor material)
metal (part material)
overall: 1.8 cm x 36.8 cm x 6.9 cm; 23/32 in x 14 1/2 in x 2 23/32 in
place made
United States: Oklahoma, Fort Sill
ID Number
catalog number
accession number
Science & Mathematics
Rule, Calculating
Slide Rules
See more items in
Medicine and Science: Mathematics
Slide Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Ben Wharton Rau and Margery Felsenthal Rau
Additional Media

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