More to consider
Lever Bros introduced Surf "heavy duty" detergent to US markets in 1948, things did not go well. By the end of 1956 "Surf" succeeded in capturing only 3 percent of the market and had lost a total of over $25 million.
Despite whatever successes Lever Bros had in UK and elsewhere in world by 1950's into 1970's their attempts at getting a foothold in US "heavy duty" detergent market were flops. There was "Vim" tablets and Wisk liquid. Of the two only latter had any resemblance of success but came at high price. Worse as anyone who used Wisk liquid then can testify the stuff made tons of froth. That wasn't doing Lever Bros. any good and they desperately needed a low suds heavy duty detergent.
Lever Bros. expertise laundry wise then largely revolved around soap based products. To wit Persil sold in UK as noted was a soap based product in 1950's well into 1970's and into 1980's.
P&G's Tide forever changed US detergent market killing off pretty much all demand for soap based laundry products outside of niche markets. Ivory Snow existed as one such "niche" product.
Lever Bros acquired the "assets" of All detergent from Monsanto, it brought them nothing but grief and lead to a legal battle as US government brought legal action to prevent Monsanto from selling All to Lever Bros. under argument it would reduce competition in laundry detergent market. Lever Bros and Monsanto prevailed so that was that. However low sales and margins still plagued Lever Bros in USA.
Seeking to right that ship Unilever dispatched their top man, Michael Angus to USA to get things sorted, and he did.
One result was launching of Surf liquid then powder detergent to USA market.
https://www.chicagotribune.com/news/ct-xpm-1987-06-04-8702110171-story.html
https://www.referenceforbusiness.com/history2/66/Lever-Brothers-Company.html
Zip Codes were introduced by USPS in 1963 and became mandatory in 1967. Box in OP gives address of Lever House (still located on Park Avenue) simply as "New York, N.Y.".
Thus my money says packet is from early 1960's a time when Lever Bros was trying quite hard to break into USA heavy duty laundry detergent market.
Notice on packet in OP OMO makes frequent use of word "heavy" obviously alluding to product being a "heavy duty" detergent. Lever Bros. didn't use such marketing elsewhere so there you are then.