Over the years I've owned a number of dynamic tube testers. Some worked better then others but all of them worked well. The one model that has always been my favorite is the Precision 10-12. This is a well-designed tube tester that was first introduced in 1947 and was the foundation model for the Precision 10-15, 10-20, 10-22, and the10-54 models. The 10-12 was designed to be portable but probably better off being used as a bench type tester. The nicely finished wooden case looks great for a tube tester but it wasn't very durable for true field usage as from the many 10-12s I've seen, over the years, whose cases were heavily scratched, stained, chipped, and overall looking battlefield worn. To find a 10-12 with a case that's in really nice condition is rare and usually expensive. A good example will usually sell for around $150.
    The one feature, that I believe, makes the Precision 10-12 stand out among any other dynamic tube tester is the range of tubes that the 10-12 can test. Precision didn't try to outdate the 10-12 by limiting the number of tubes that it could test but, instead, constantly updated the tube data right up to the early 1960s.
    In the 1960s Coletronics Service Inc. began manufacturing a number of adaptors under the brand names of Precision, Eico and Coletronics which would test later developed tube types such as the 10 pin Decal, the 10 pin Miniture, the five pin and the 7 pin Nuvistor, the Novar and the Compactron. These adaptors extended the 10-12s ability to test a much wider range of tubes and, therefore, Coletronics published more tube data publications for the 10-12 in the form of booklets and supplements.
    Today the 10-12 can test tubes issued from 1920 on up to 1975 and beyond, a feat few tube testers can boast. My Precision 10-12 can test more tubes then my Hickok 529C, Hickok 6000 with CA-4 adapter, Precise 111 and my Triplett 3444 mutual conductance tube testers even with all their supplemental data and tube adaptors. Only my Hickok AN/USM-118B cardmatic tube tester might have a wider range.
    I bought my Precision 10-12 from MAI/Prime Parts, a electronics retail and surplus store located in Indianapolis, Indiana. I bought it for the specific reason of using it as a field tube tester whenever I attend hamfests, antique radio swap meets, etc. I'm confident that any tube I come across, that my 10-12 or tube adaptor will accommodate, I'll be able to test it.
    I buy and sell a lot of tubes and so I need two tube testers, one to help me buy my tubes and one to help me sell my tubes. I use my 10-12 to test tubes that I plan to buy since I only need to know if the tubes are either good or bad. Later when I sell my tubes, which is usually do on ebay, I'll test them on either my Hickok 539C or on my Triplett 3444 mutual conductance tube testers and post the results on my auctions. I believe perspective tube buyers tend to buy with more confidence tubes that have been tested on high quality, mutual conductance, tube testers rather then on simpler dynamic tube testers.

Tube and Rectifier Line Up:
5Y3-GT.....Rectifier

Power Source:
AC...117 Volts

Dimensions:
Height...7-3/4 inches
Width...18-3/16 inches
Depth...7-3/4 inches

    This owners manual covers the introduction and summery of features, functions and description of controls, switches, levers, etc.,operating instructions, Ballast information, qualitative paper condenser tests, battery testing instructions, service notes, general notes and information, principles of "Electronamic" tube testing and schematic diagram.  The manual measures 11 inches x 8 1/2 inches and contains 17 pages, excluding front and back covers.  The cover is copyrighted 1950 and the inner pages are copyrighted 1952. Measures 8.5 x 11 inches.

    This supplement covers tubes that are deemed as obsolete, infrequently encountered, and having special / limited applications. Over the years Precision published several versions of this supplement, each with it's own code number that corresponded with the most current roll chart at the time. Example: a supplement with a code of (AB) was meant to be matched up with roll chart  MRC-(A2B) or a supplement with a code of  (EF) was meant to match up with roll chart  MRC-(E2F). Measures 8.5 x 11 inches.

    This booklet covers infrequently encountered tubes types, obsolete tube types, tubes manufactured for special or limited applications, Western Electric tubes and forign tubes. Some of the tubes listed require a socket adaptor for testing. This booklet is good for use with Precision models 10-12, 10-15, 10-20, 10-22, and 10-54. Measures 7.5 x 5.5 inches.

 
    The Addendum is an additional data supplement to be attached to the MRC supplement booklet (GK). It consists of 6 pages, 5 pages covering the additional American and foreign tubes and 1 page consisting of a a list of the American equivalents of foreign tubes that are listed on this and various past supplements. This supplement is dated 3-61. Measures 7.5 x 5.5 inches.

    This socket adapter was designed for the older model Precision and Eico tube testers so that they would be able to test the newer tubes that were on the market during the 1960s and 1970s. This adapter features tube sockets for 10 pin decal, 10 pin miniature, 5 pin Nuvister, 7 pin Nuvistor, Novar, and Compactron tubes. Coletronics manufactured tube adapters under the brand names of Precision, Eico and Coletronics.

    This 16 page booklet covers all of the tubes that would have normally been found on a Precision roll chart. The tubes listed in this booklet were considered to be all of the tubes that were currently still in use at the time of booklet's printing. This booklet was originally offered in spin bound form and it's measurements are 8.5 x 11 inches. spin bound form and it's measurements are 8.5 x 11 inches.

    This 42 page booklet covers all of the American and foreign tubes that require the use of the Coletronics A-15 tube adapter along with additional tubes that could be tested by the tube tester itself.  There are a few special European 8 pin minature tube listings that require the usage of the Coletronics G-118 magnoval adaptor to test them. This booklet was meant to be a supplement to the MRC series Roll Chart booklet and was offered in spin bound form with the measurements of 8.5 x 11 inches.

    Coletronics periodically issued 2 page fliers to update the Tube Data 4-1-74 booklet with the latest tubes. I have three such fliers which are dated 7-15-74, 2-15-75, and 11-1-75 respectively. The latest known update is 2-1-78. Measurements are 8.5 x 11 inches.

    This 2 page manual covers the general operating instructions and test values for using the 12 pin Precision CRT Tube Adapter. This manual covers all of the test settings for Precision models 612, 614, 620, 654, 910, 912, 914, 915, 920, 922, 954, 10-12, 10-15, 10-20, 10-22, and 10-54. Measurements are 8.5 x 11 inches.