Sam and Dave, n. — Green’s Dictionary of Slang

Sam and Dave n.

[soul singers Sam Moore (b.1935) and Dave Prater (1937–88)]

(US black) the police, when working in a team of two.

1980		E. Folb Runnin’ Down Some Lines 67: Characteristic of the police-related lexicon is an ironic, if sometimes grim, humor that is embodied in names like [...] Sam and Dave (partners in a patrol car).
2001		OnLine Dict. of Playground Sl. 🌐 Sam & Dave n. Police Officers. The expression is used as follows : ‘Can you see those Sam and Dave’s in the Caddy?’.