Sentence:  ... a small steel pistol was concealed within the purse, the trigger of which was connected with the mounting, and made part of the machinery, so that the weapon would certainly be discharged, and in all probability its contents lodged in the person of any one, who, being unacquainted with the secret, should <WSD>tamper</WSD> with the lock which secured its treasure. 
Meaning of the word marked with <WSD> tags:  To make unauthorized or improper alterations, sometimes causing deliberate damage; to meddle ("with" something).