60 Day 100% money back guarantee. Precision chrome-on-glass calibration plate manufactured by Santa Barbara Engineering Inc. (SBE). The 4" × 4" × 0.050" square presents dark-field geometry with clear circles (.025, .030, .035 in) and clear lines (.015, .010 in) for microscope and machine-vision resolution verification. Serial number 20240, last certified 9-8-1997 for Hutchinson Technology; original calibration report included. Mirror surface is bright with no scratches in the active area; only faint handling marks at the perimeter. Supplied in its dovetailed wood case with foam insert and twin-latch hardware. Ideal for QA labs, optical R&D or metrology teams that require traceable ten-thousandth-inch features. Ships from Carol Stream, IL in double-boxed protective packaging to preserve alignment and finish. Keyword Block: sbe calibration plate, dark field target, optical resolution standard, 4x4 inch chrome glass mask, santa barbara engineering, metrology test chart