The 2 m subtense bar from Zeiss Jena is a 2 piece light metal tube which you can stuck together via s screw flange. The ends of the tube have targets at exactly 2 m separation. They can also be illuminated electricaly with an illumination set. You will receive also the illumination set (grey color), but accumulator (storage battery) is unfortunately NOT a part of the set. The small lamps were normally equipped with small 2,5V 0,2A bulbs. Inside each half of the rod there is an invar bar for temperature compensation. Invar (nickel-iron alloy) is unique in its resistance to the temperature changes, so unlike other metals it will not expand or contract. Subtense bar is also called parallactic bar, because it was used as a base for measuring parallactic angle with precision theodolites, like for example THEO 010. Once all is set up, observer will measure the angle from his position to each end of the 2m markings on the subtense bar, do some calculations and he will get the distance from the observer to the centre point of the bar. Subtense bar was made in the early 70's. Color of the bar is grey. MPN: 39115. Rare special quality edition: Q1. Made for the needs of the Czechoslovak armed forces. Conditon: rare unused - excellent condition. Wooden transport box is in good condition too (fully serviceable), the grey color is already peeled off from the outside of the box (moving inside the stock and very long storage) , but from iside the box is like it was made yesterday. All the accessories and pouches are in perfect new old stock condition - never used. Accessories: illumination set (grey painted) in original canvas pouch with leather attachments. Tribrach in original canvas pouch with leather attachments. Plumb bob is still packed in a paper. Subtense bar (2 pieces) is packed in original canvas bag with leather straps for carrying on the back. Of course you will receive also the original distance table in 4 languages and the protection cap for the top libella. Please take a closer look at the detailed gallery pictures of the relevant set. Please also note, that the wooden tripod in the picture no.3 is NOT for sale and was used for full display purposes only!