The exact same oxygen regulator as the 25-100C-540 normally priced at $79.99. This one just has a plain looking label not the typical one used today.  It is new, old stock & there are very few available.  The one-piece enclosed design has an internal filter and a PTFE Teflon seat.  A brass plated bonnet covers the solid forged brass body. It is equipped with 2 inch dual scale gauges. It has a delivery pressure range of 0-100 & a supply pressure gauge of 0-4000.  Harris regulators have a 3 year manufacturer's warranty.