TRINER
AIRMAIL-ACURACY
2 Lbs
letter scale

Triner 2 Lbs Airmail-Accuracy letter scale

This is a Triner letter scale that was produced for many years and in large numbers. Small variations in model emerged over the years; see, for example, this smaller one shown earlier Triner Air Mail Accuracy. A few more variants are pictured there. This Triner model is still frequently offered second-hand on auction sites. This is because many were produced, and especially because it is an extremely solid and robust scale. They are available with a range of 8 ounces, 9 ounces, 16 ounces, and even heavier versions of 2 lbs and 4 lbs. There are also versions with separate add-on counterweights, allowing them to weigh up to 6 lbs or up to 12 lbs. For the metric world, there are models that weigh up to 250 grams, 500 grams, 1 kilo, or 2 kilos, subdivided in increments of 5 or 10 grams. In addition, there are at least thirteen models with bowls and trays specially shaped for shops, some with two weight beams, coarse and fine, and other versions with separate add-on weights.

back of the Triner Airmail-Accuracy letter scale

Triner is an American company and was founded by James M. Triner of Chicago, Illinois in 1902. Prior to that, James Triner initially worked for a few years at Pelouze, another manufacturer of scales.
The Triner shown here has an American postal rate card; according to the rate card, those rates came into effect on October 1, 1951. Strange, because the American letter mail rate of 3 cents per ounce was kept the same from 1932 to 1958. However, on October 1, 1951, the shipping rate for catalogues weighing between 8 ounces and 10 lbs changed—the Fourth-Class Catalogs tariff—which may explain this date.
I have not (yet) found a patent for the design. However, I did find a short article in Office Appliances 1933-02 vol 57 iss2 on pp. 19-20 in which this Triner is described as a new type of Postal Scale. I also found several advertisements from 1933 and 1934 in which the Airmail-Accuracy Triner is presented; see the bottom of this page. The Triner on this webpage is of a more recent date; there is no longer a small airplane on the Triner logo, whereas the first models from 1933 did have one on the logo.
This Triner weighs up to 2 lbs, or 32 ounces, and the scale is divided into quarter-ounce increments. There are also 2 lbs versions divided into half-ounce increments. During weighings, one compares whether it weighs more than the value set with the counterweight, until it weighs equal to or slightly less than the set value. One then reads off the postal rate corresponding to that set weight.
The scale is 41.5 centimeters long, 16.1 cm wide, and 17.6 cm high. The letter plate is 14.5 x 14.5 cm. The scale weight is 2878 grams.
Below are some images of this Triner Airmail Accuracy letter scale.

side view

animation: both sides have a measuring scale [move the pointer over the photo]

side view

the factory name + patents applied for and no. 9	the Triner logo and the model name Airmail-Accuracy	the zero adjustment screw
the movable counterweight and the quarter-ounce slots	the movable counterweight at zero ounce	the counterweight beam with the quarter-ounce slots
with 1 Lb on the plate and the movable counterweight still at zero Lb	animation: balance the scale to 1 lb [move the pointer over the photo]	without the weight on the plate, the counterweight still at 1 lb
with 2 lbs on the plate, the slide still at 1 lb	animatie: balance the scale to 2 Lbs [move the pointer over the photo]	With the 2 lbs weight on the plate, the scale is balanced
the counterweight to the far right = 2 lbs	the different types of mail and associated rates	the various types of mail and associated rates up to 2 lbs
the Triner letter scale with the postage rate card	the Triner letter scale with the postage rate card	The rate card was valid from October 1, 1951.
the plate for letters and other mail to be weighed	top view	the open bottom of the letter scale

Triner advertisement in Office Appliances 1933-02 vol 57 iss2 pp 86

Triner advertisement in Office Appliances 1934-06 vol 59 iss6 pp 90

a two-color advertisement for the Triner Airmail-Accuracy [internet source]

Airmail-Accuracy Triner, on a catalog page of Hibbard, Spencer, Bartlett & Co from 1933

the large 2 Lbs Airmail-Accuracy with the smaller Triner 1 lb, see here