Serial number 51978 was ordered on October 7, 1932 by Chicago Musical Instrument Co. It stamped on October 11, 1932 and cleared final inspection on October 22 that year (only 11 days in production!)

The neck is a replacement.

Style 18 features:

Back and sides: Mahogany

Top: Red spruce (Adirondack)

Purfling: Lines

Binding: Black celluloid

Other period features:

Scalloped X-bracing

Ebony fingerboard

Ebony belly bridge

Ebony neck reinforcement

1-27/32" neck width at nut

Tortoiseshell celluloid pick guard

Dot fingerboard inlay

Style stamp

Photos courtesy of Carter Vintage Guitars

At the time of writing (August 14, 2019) this guitar is available at Carter Vintage Guitars (https://cartervintage.com/products/martin-d-18-2009)