Invar

(Engineering / Metallurgy)™ an alloy containing iron (63.8 per cent), nickel (36 per cent), and carbon (0.2 per cent). It has a very low coefficient of expansion and is used for the balance springs of watches, etc.

    Invar - an alloy of iron and nickel having a low coefficient of thermal expansion; used in tuning forks and measuring tapes and other instruments
trademark - a formally registered symbol identifying the manufacturer or distributor of a product
alloy, metal - a mixture containing two or more metallic elements or metallic and nonmetallic elements usually fused together or dissolving into each other when molten; "brass is an alloy of zinc and copper"