"Keep tabs on"

Does anyone know the origin of the phrase "keep tabs on" (to monitor)?

It comes from keeping accounts, maintaining records of charges. The Oxford English Dictionary labels "tab" in this sense as U.S. colloquial and defines it as "A table, an account [cf. TABLET . . . ]; a check." The earliest use of the phrase recorded in the OED is dated 1889: "Every man keeps a mean little tab in his head on his fellows" (Washington Post).

Why am I doubting that the Washington Post should be the first use of the word 'tab'?

Bearing in mind that inkeepers/publicans kept a note of credit given to customers on slates and an alternative word for a writing slate is 'tablet'- it seems implausible that the WP was not simply recording a long-used expression. Anybody know?