Lugs are generally made by an outside supplier to a bike fabricator. If enough are ordered a "special" feature might be worthwhile. Cut outs in various shapes is a common feature to be played with.

Can you be more specific as to the cut out shape and locations? Do you know the frame's threading? Shots of the lugs, crown, BB shell, seat stay tops and stay ends would all help to eliminate possible brands but without more hints the range is still pretty wide open. Andy