Unusual armourer tools and Lee Metford/Long Lee/Martini Enfield foresight covers

[Nigel]

I picke dup a few things today but I'm struggling to identify some of them - all input would be gratefully received.
In no particular order:
1. A Salter spring weight weigher which is similar to those used with the Lewis MG but this is made of steel and the T-Shaped addition looks as though it would fit on the end of a wooden rod. It is Broad Arrow marked.
2. A brass implement with a scribe attached on a chain. You can see the Broad Arrow marking and Crown above INO above 303.
3. A bore inspection mirror for something like .50 Cal but unlike others I have seen, especially with the two rivets and a screw at the rear.
4. A couple of Protectors, Sight which could be used on Lee Metford, Long Lees and Martini Enfields. One is Broad Arrow marked and has the Serial No. 611