[jeffschevelle]

The white BEST WAY TO PROTECT YOUR ENGINE ink stamp was used from approximately March 1968 through at least November of 1974 based on original filter and NOS air cleaner assembly box dates.

The earliest PROTECT YOUR ENGINE (without BEST WAY TO at the beginning) filter I have documented was in a box with 1975 date (no month or day).

So if the ink stamp just says PROTECT YOUR ENGINE (without BEST WAY TO), then the filter was made no earlier than December of 1974, at the earliest.

Note that there are filters being sold on ebay where it is obvious that the BEST WAY TO has been added with a separate stamp, to make a later filter look like an earlier one ...

As to the mesh, the horizontal / vertical version of the soldered wire "square mesh" was the second version of that wire used. The first version was the exact same soldered wire with square-holes, but it was cut so that the wires were oriented diagonally on the completed filter. It was in use at least as early as 1960.

I have not pinned down the exact changeover date from diagonal "square mesh" to horizontal/vertical "square mesh", but the latest dated box with a diagonal mesh I have documented is 7/14/1969, and the earliest horizontal/vertical mesh I have documented was in a box with 1970 date (no month or day). And obviously both of those were BEST WAY TO filters since made before 11/1974.

Happy hunting!