A new addition to my collection, a HP 150A oscilloscope with 151B high gain amplifier plug-in. I have given it a clean inside and out as it was very dusty and interestingly found a few replacement Tek valves fitted, presumably during past servicing/repairs.
Its a late model from the last 2 years of production (S/N prefix 048), the 150A appears to have had a bad reputation for being very unreliable, but they must have built quite a lot of these though as the serial number on mine is over 4000.
More information on the HP 150A here at the HP memory project;
http://hpmemoryproject.org/news/150a/hp150a_page_00.htm
David