Antique master butter knife measures 7 1/4" long.   The blade is faded, but I can make out:
J.H. (?) Smith & Co  LIMITED (a number) Warranted 18 DWT Milton, PA 

It weighs 58 grams

It has been kept in a flatware chest ~ from a smoke-free home. 

Please see photos ~ there are very faint scratches and signs from use