|Name and Model Number||Psychrometric Computer|
|Country of Origin||USA|
|Date of Manufacture||unknown|
|Front Scales||Relative Humidty – High Scales|
|Back Scales||Relative Humidty – Low Scales|
|Scale Length||11.35" diameter|
|Type of Rule||Disc|
|Construction||Plastic on aluminum and plastic discs|
|Area of Use||Technical|
|Comment||For calculating relative humidity.
Made for the Bureau of Aeronautics by Virginia Plak Co., New York.
The Smithsonian Institution has a similar calculator by a different manufacturer.
|Donor||Collection of Clay Castleberry|
(Click Picture for Details)
|In conjunction with our 'donors' we assign a rarity rating to each item, based on the system devised by Herman van Herwijnen|
|(1929 - 2004), renowned Dutch collector, author, and creator of Herman's Archive, a collection of 5,000 slide rule images on CD.|
|• RR = Rare - 1 of 25 collectors has one; it may take a year to find an example in the marketplace.|
|• RRR = Very Rare - only a few known to collectors; may be several years before it comes up for sale.|
|• RRRR = Extremely Rare - a museum piece; unlikely that an example will come up for sale.|