Here is a folding rule. The manufacture is Stanley Rule and Level Co. (picture 7). The model is No. 53 1/2 (picture 7). The rule is very old. Through this knowledge, https://www.davistownmuseum.org/bioStanley.htm I estimate this rule was made in 1860s to 1870s as it is No. 53. 

The rule seems once broken (picture 11) but it was restored properly (picture 11). The mechanical system is still working properly (picture 3, 4, 5, 6). The 2 sharp pins (picture 8, 9) are still on the rule. The rule unit I think it is 1 inch. I use a modern rule to compare the folding rule (picture 12).

The folding rule is a real antique. Through USA laws, an item is over 100 years, it can be considered as antique. The company Stanley Rule and Level Co. (picture 7) was built in New Britain, Connecticut (picture 7). Connecticut is a state in the USA. The company's name 'Connecticut' was used until 1900s. So, the rule must be a real antique.

Happy to buy the folding rule!!