The Sony Dynamicron range was a series of high quality Japanese made video cassettes. These preceded the introduction of the Dynamicron DX. They were very solidly built, and housed in sturdy cardboard jackets. These probably date back into the 1980’s. They had a multi-coloured stripe, the older jacket with the original labels plastered over the top looks like this:
The later jacket looks like this:
The cassette has a pale green clip and blue tinting, with frosted appearance. The underside features a slight alteration to the regular screw pattern, and the manufacturer’s batch code area is printed in thick bold lettering.