From BGG description and the included rulebook. The rulebook is copyrighted 1968 in this version, the Market Price Calculator is copyrighted 1968 in this version, the Stock Market board is marked "New Improved", and all other components are copyrighted 1964. The serial number for the Market Price Calculator is C-B170-C88, and the Rulebook has serial number C-8170-R70.
Another 1968 copy of the game includes the "Margin Variant" and "Bear and Bull Market" rules updates but the stock market board is not marked "New Improved" and the serial numbers listed are different. The rule book has serial number C-B170-R68A and the Calculator has serial number C-B170-C68 and is copyrighted 1968.