ETA offers Electro Chemical Etching Machines for marking monograms/ part number on the valves. Two types of machines are available- Static and Rolling head. In the latter the job rolls under the etching head and the characters get etched on the job. Etching on the complete periphery of the job is possible. Here etching on chrome-plated surfaces will not be effective. In Static Head machine, this problem is over come; but etching is possible only on an arc of 120 degrees on the periphery of the job.