National Coal Board  N.C.B. Metric Methane Calculator

National Coal Board  N.C.B. Metric Methane Calculator

Metric Methane Calculator.
National Coal Board  N.C.B. Metric Methane Calculator.
Made from Plastic and Brass with a P.V.C wallet. Size 6″ inches diameter.

It has 4 revolving calculating discs on the front and 1 on the back.

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