Tag: cartography

• Revision Index Filing

  Mirror Spring etiquette for filing REV A and REV B on the same corridor—late chisels, amendment throats, and offset witnesses that force two indexes to admit the same footsteps.

• Stratum Gauge Cards

  Mirror Spring field instruments: laminated glass cards scored with charter meridians, used to read buried salt strata when compass needles drink starlight instead of north.

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