This is one Lot of New RF Bay, Inc. 3.5mm (male) to 2.4mm (female) DC-33GHz Precision  Adapter. Part Number: A350M240F. .

Components manufactured in Switzerland, assembly and tested in China, this high performance Microwave Precision Adapter provides test equipment need for high quality and low cost solution.

Data sheet:

http://rfbayinc.com/upload/files/adapter/a350-240.pdf