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Pocket Transits
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"A comparison table of serial numbers and features observed online to be used as an aid to determining age"
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This spreadsheet is a compilation of serial number and feature data first put togetyer by William J. Hudson and presented on his excellent website 'Brunton Pocket Transits'. Sadly, Mr. Hudson's website is now off-line and for several years his information was unavailable to those interested in the history of the pocket transit. Over the past few years I've written several articles about pocket transits on my blog at www.oldtopographer.net, and referenced Mr. Hudson's web pages. I've been contacted several times by readers who were interested in Mr. Hudson's information but couldn't find it on the web. In early 2013 one of my readers was able to find the archive of Mr. Hudson's web pages on the 'Wayback Machine' web archving portal and I was able to find Mr. Hudson's contact information on one of the pages. He graciously gave me permission to use his website information and share it out to the collector community. This spreadsheet was put together to provide the serial number and feature data in an easy to use and update format and to serve as a launch point for future compilation of pocket transit data.

Brian Haren
oldtopographer@gmail.com
www.oldtopographer.net
April 2014

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From the original introduction by William J. Hudson:
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I began this page as a way to help me assign approximate dates to various pocket transits as they came up for  sale on ebay. Any assistance that you  can give in filling in some of the blanks would be most helpful, both to me, as well as to other Brunton collectors. Some  of the blank areas in the table are features that I did not observe at the time,  or features that I could not observe due to the information available. Dates: I describe the dates in one of three ways. A date followed by a plus sign (+) indicates a beginning date of a possibly open ended range. For example, a Brunton which  has an engraved patent number will give us a date that the unit cannot be older than. Obviously, if a patent was  assigned in 1914, and the patent date or patent number is engraved on the unit, it could not have been made in 1894. A second method is a date by itself. This occurs only when a date is firmly established by an engraved date or date code. A third  method is a pair of years, which gives a possible range of dates. This occurs in the Brunton Company line, for example: We know the Brunton Company was established in 1972, and we know that  they changed their serial numbering system in 1985. Therefore any units with an older serial number type must have been manufactured between 1972 and 1985.
Abbreviations:I have used some abbreviations in order to make the table more manageable.

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Dates: I describe the dates in one of three ways. A date followed by a plus sign (+) indicates a beginning date of a possibly open ended range. For example, a Brunton which  has an engraved patent number will give us a date that the unit cannot be older than. Obviously, if a patent was  assigned in 1914, and the patent date or patent number is engraved on the unit, it could not have been made in 1894. A second method is a date by itself. This occurs only when a date is firmly established by an engraved date or date code. A third  method is a pair of years, which gives a possible range of dates. This occurs in the Brunton Company line, for example: We know the Brunton Company was established in 1972, and we know that  they changed their serial numbering system in 1985. Therefore any units with an older serial number type must have been manufactured between 1972 and 1985.
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Abbreviations:I have used some abbreviations in order to make the table more manageable.
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Body Codes: 2 letter  material, optional 3 letter finish
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Al: Polished Aluminum
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Al/Blk:  Aluminum, Black paint
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Al/Grn:  Aluminum, Green paint
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Al/Brn:  Aluminum, Brown paint
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Al/Gra:  Aluminum, Gray paint
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Co/Wht:  Composite, White
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Co/Grn:  Composite, Green
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Level Codes
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1L: 1 Long Level
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2L: 2 Long Levels
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1L1R: 1 Long Level, 1 Round Level
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1L1R/Y: 1  Long Level, 1 Round Level, Yellow "High Visibility" fluid
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Graduations: I will be  describing the graduations as "D" for Degrees, "Q" for Quadrants, and "M" for Mils. Unless otherwise noted, "Degree" scales are from 0-360 counter-clockwise, marked every 10 degrees with tick-marks at each degree. "Quadrant" scales are from 0-90 in each quadrant, marked every 10 degrees, with tick-marks at each degree. "Mil" scales are from 0-6400, marked every 200  mils, with tick-marks at each 20 mils.
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Q: Quadrants
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D: Degrees
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M: Mils
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Clinometer Codes:Clinometer scales are marked in Degrees, grade, and Mils. Later  models may have more than one scale, so I've noted the number of scales, and  the number of supporting arms. Degree clinometer graduations are every 10 degrees with tick-marks by degree. A vernier scale is usually located on the swinging arm which is graduated with tick-marks every 10 minutes. Grade scales are marked every 20%, with tick marks every 5%. Mil clinometer graduations are marked every 200 mils, and there does not appear to be a vernier on most models. The codes are in the format: 2 characters arm type, 2 characters scale type, 1 or 2 characters graduations. Note that on models with more than one clinometer scale, the position of the letter denotes which scale is on top as  the scale is being read.
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1A1SG: 1 arm, 1  scale, grade
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1A1SD: 1 arm, 1  scale, degrees
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1A1SF: 1 arm, 1  scale, fractions (grade)
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1A2SDG: 1 arm, 2 scales, Degrees over Grade
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1A2SGD: 1 arm, 2 scales, Grade over Degrees
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2A2SDG: 2 arms,  2 scales, Degrees over Grade
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2A2SGD: 2 arms,  2 scales, Grade over Degrees
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Sights: I describe the  sight types as this is an important indicator especially in the Ainsworth line. The two sight types are "1 hole" or "2 hole". The "2 hole" sights are  the 'figure eight' or 'dual intersecting' sight holes. The code is 5 characters, where the first two describe the number of sights, the next two  describe the sight hole type, and the last character describes where the short sight (if present) folds.
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1S1HN: 1 sight,  1 hole, None
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2S1HO: 2 sights, 1 hole, Outside
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2S1HI: 2 sights, 1 hole, inside: Common on K&E models
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2S2HO: 2 sights, 2 hole, outside: Common on Ainsworths
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2S2HI: 2 sights, 2 hole, inside: Late models by Ainsworth and nearly all "Brunton Company"  models
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