Green’s Dictionary of Slang

(US Und.) insecure, vulnerable to theft, rickety.

1948		H. McCoy Kiss Tomorrow Goodbye in Four Novels (1983) 83: Bums like Floyd and Karpis [...] who were getting rich off cracker-box banks.
1951		Kerouac On the Road (The Orig. Scroll) (2007) 355: Crackerbox towns with a sea for the end of every street.
1960		(con. 1950) R. Leckie March to Glory (1962) 108: Those ‘cracker-box’ ambulances [...] clogged with the wounded.