The listing, Model RR Scale Ruler has ended.
Scale ruler for HO and O scale modeling
MODEL RAILROAD REFERENCE RULE
This is a stainless steel (NOT aluminum like they sell today.) scale ruler, 12 inches long by 1 inch wide.
It is General Model No. 1251, made in U.S.A. (You can't hardly find that no mo'.).
Markings are etched and anodized in black. It has seen year of use and markings are all perfectly legible. (I cleaned it up with a bright boy and didn't lose a marking.)
The face contains measurements for HO scale (3.5mm = 1 foot) and O scale (1/4"=1 foot.)
The back is a wealth of useful information:
- Decimal Equivalents for fractional drills (1/64" to 63/64") and Number drills (#1 to #80).
- Tap drill sizes for small screws (00-90 to 6-32).
- Formula for 75% depth of thread.
A 5-inch ruler in 64th inch increments and a metric ruler, 1 to 10 cm in mm increments.
Similar items (but aluminum) on ebay are $8 to $14.
See: http://tinyurl.com/2bj8gff