Micro optical pyrometer - disappearing filament type

What is for sale: Micro optical pyrometer - disappearing filament type

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This is a Micro Optical Pyrometer made by The Pyrometer Instrument Company.
* "disappearing filament" type micro optical pyrometer
* especially suitable for measuring the temperature of small targets
* temperature range: 700 - 3200 °C (1300 - 5800 °F)
* includes lenses A, B, C, D, E, and F (see the Pyrometer Instrument Company web site for working distances & suggested target sizes)
* appears to be complete and in working order
* see additional details and discussion in the text following the pictures
(Click on thumbnails below to view higher quality images.)
This is a "disappearing filament" type optical pyrometer. The seller could describe how such a device works, but he prefers to simply direct the interested reader to the Pyrometer Instrument Company web site. The linked page is for an instrument that the same company still produces which operates on the same principles (though now available with more modern electronics!) as the one offered here. They provide there a description of the nature of the instrument, its advantages, and some typical applications.
According to the manufacturer, the serial number on this unit indicates that it was manufactured in the early 1960s.
Cosmetic condition of this equipment is good, but not pristine. The pyrometer shows a few scuffs and scrapes (most noteable is one visible in the pictures on the right hand side of the front telescope tube). Also visible in the pictures is some residue on the top from old adhesive tape. Some of the lenses could use some cleaning, but the seller feels that it's better to leave that sort of thing to the new owner, lest he unintentionally damage something through ignorance. The plastic face of the meter has a few small scratches in it, but nothing ghastly. The kit case and the contents all have the sort of smell that the seller associates with old instrument cases. There is a stain visible in the back right hand corner of the case, and the hinge on that side shows some corrosion; perhaps a battery leaked in the case at some time during its life. As seen in the pictures, the case shows some wear on the outside, and is missing one of the steel "buttons" on the bottom.
The tripod appears to have been modified by a previous owner, to the extent that the center column appears to have been replaced with a taller one machined from a piece of aluminum round bar. This bar doesn't fit snugly inside the collars, but the tripod is steady enough once the thumbscrews on the collars are tightened. Additionally, this center post doesn't allow the pyrometer to be positioned any lower than shown in the pictures. If one were putting this pyrometer to work, the user might consider either fabricating a new center column to suit, or, better still, making an adapter to allow the pyrometer to be mounted on one of the nice tabletop tripods that are readily available.
The cable for connecting the battery, meter movement, and pyrometer is clearly not the original cable, based on the (modern) look of the crimp-on spade terminals that were used in its construction.
The seller has operated this instrument, using it to measure the temperature of a lamp filament. It works as he expected based on what he had read at the manufacturer's web site. As the rheostat is dialed up, the readout on the meter rolls up smoothly, and the filament heats up. It's straightforward to adjust the rheostat until the apex of the filament "disappears" where it overlaps the target of interest. The human eye really is pretty good at this sort of thing; the filament "disappears" only over quite a narrow range of indicated temperature.
The seller does not have a reference lamp to calibrate this unit, but he did check the meter movement using a precision DC current calibrator. The scale of the meter has two reference points marked on it. To align the needle with the "53 mA" mark, an indicated current of 52.8 mA was required. To align the needle with the "103 mA" mark, an indicated current of 102.8 mA was required.
The battery was found to read about 4.25 V as checked by a digital multimeter - and did not "close up shop" when the pyrometer was in operation (voltage did not collapse under the load of the filament).
Questions - please ask. Thanks for looking!