The 616239 is the source lamp (light bulb) for the 755 series paramagnetic oxygen gas analyzers. It was sold in kit form (the lamp and a set of instructions) as 616418.
RIGAS has a replacement for this NLA (no longer available) part. Call us!
Your 755, 755G, 755A, 755R, and 755EX are NOT obsolete. As long as you don’t destroy your detector (dumb-bell assembly) we can maintain this unit for many, many years to come.