M.F. Christensen and Son (MFC)

M. F. Christensen & Son Co., usually shortened by collectors to MFC, was one of the earliest American machine-made marble companies. Best known for its slags, the company produced marbles with white or lightly tinted bases layered with flowing bands of color, often in rich and distinctive combinations. Many examples show soft blending, depth, and a handmade look that appeals to collectors.

Condition is especially important with MFC slags, as strong examples with clean surfaces and sharp visual contrast are far less common than played pieces. Today, MFC marbles remain desirable for their early production history, classic American glass, and the quiet beauty found in their better color combinations.