Some older cameras used batteries like this one.

http://www.smallbattery.company.org.uk/index.htm?http://www.smallbattery.company.org.uk/sbc_cr2.htm

Have a look what type it is and Google it.

Threes nothing strange about a non rechargeable lithium battery for an old film camera.

I have an old camera that uses them

 

Dust on the mirror shouldn’t be a big problem.

 

Yes its worth tying it out, if only for curiosity sake.

Enola

Full Time Professional Photographer