Andrea–Thank you for the expanded information. With that I can now give you a much fuller answer. Just as a note, we on this Forum are very glad to help in any way we can. But, since we are a very detailed group, we need ALL the details you can provide if you want a knowledgeable answer. For instance, in this case, knowing if the case was brass or copper is critical in dating it. Copper cases were only used up to 1942 and after WW-II only brass cases were used. Some loads were made in brass prior to WW-II, but NO US .22 Long Rifle were made using copper cases after WW-II.
Now back to your case. I assume you are working a Cold Case File. First of all, the examiner who said “the only Winchester manufactured ammunition with copper coated bullet in that era was loaded on “Super X” headstamped brass.” was incorrect. The “Super-X” headstamp was used on Western brand not Winchester.
However, Winchester and Westen are both the same company, just different divisions of Olin Corp. The name of the company in 1968 was "Winchester-Western Division, Olin Mathieson Chemical Coropration. But the products were boxed and sold under the seperate brands of “Western” using the “Super-X” headstamp and Winchester Super-Speed using the “H” headstamp. Other than the box and the headstamp, the cartridges were identical for both brands and were made in the same factory on the same machines.
If you are looking for a box of this 1968 ammunition, the box style used from 1962-1971 is yellow with a big red “W” behind the words “SUPER SPEED”. On the left end of the top are printed verticaly the words “WARNING Keep Out of Reach of Children” The Load Index code is “SS22LR”.
However, this same cartridge was made fro 1945 until about 1990, only the boxes are different.
If you need more detail or other information, don’t hesitate to ask.