Hi dannyk13,
Good to hear from you again.
I should also point out that a 'peterman' is slang for safeblower, possibly derived from saltpetre, an element of gunpowder, used by early safe blowers. (Personally, I preferred gelignite, but that was before I became a respectable crossword compiler.)
You were bang on(!) with Peter being slang for safe (or even cell apparently).
Kind regards,
CJR