That number does not fit the normal Western lot numbering system. However, the box is definitely post-WWII (Division of Olin Industries, Inc., is post-1944). In 1954, the name was changed to the Olin-Matheson Chemical Corporation. Therefore the box would have to be in the 1944-54 period. That is the best I can do.
The normal Western system uses a dating code something like LLnn, for example, KE41. KE would be a letter code for the loading year(K) and month(E) and 41 would be the reverse day, 41 being the 14th day. The year code letter repeats every 20 years.
3571P is probably an index or identification code indicating that specific product. For example, 357 is the caliber and 1P could be the bullet weight and type. You might look carefully at the box to see if there is an LLnn code stamping somewhere. It may also have some leading letters or numbers unrelated to the date code.