Shame all the old pics in this old post are gone. There will be disagreements I am sure, but for many years I have been saving pics of original filters in cars, and NOS filters in dated boxes, and NOS filters from complete NOS air cleaner assemblies, and have been keeping track of the data. Based on that, the progression of the style of 212 filters appears to be:
Version A. Square soldered mesh, oriented diagonally. There is NO SILK SCREENING on these. The A212CW is molded or embossed into the top of the black rubber part in large outline style font.
This version was used at least from 2/1965 through at least 8/1967. (I have originals from a Feb built 65 396 Impala that had the earliest known 396 engine assembly stamp date, from a 2/67 built Elcamino, and from a 5/67 built Malibu; and an NOS filter from an NOS 67 Camaro air cleaner assembly in GM box dated 8/1967).
Version B. NOS filter in box dated 3/9/1968 - Same filter as above with the embossed A212CW, but it ALSO has the white BEST WAY TO PROTECT YOUR ENGINE ... silk screening. This gives a good idea of the approximate date that the BEST WAY script first came into usage, since they still had some of the prior 65-67 style filters with the embossing on hand when the silk screen was added.
Version C. Square soldered mesh, oriented diagonally. Does NOT have the A212CW embossed into the black rubber part. Has only the white BEST WAY TO PROTECT YOUR ENGINE ... silk screening.
I have examples of Version C starting with box dated 9/1968, and going all the way up to box dated 7/14/1969.
Version D. Square soldered mesh, oriented horizontal / vertical (what people call "square mesh"). Has white BEST WAY TO PROTECT YOUR ENGINE ... silk screening.
The earliest dated box with one of these I have seen is 5/1970. So the change in the orientation of the wire apparently occurred some time between 7/14/69 and 5/70.
And I have examples of Version D going all the way up to boxes dated 11/1974.
Some of the earlier ones of Version D (including the one in box dated 5/1970) have a small embossed A212CW in small plain font (not the large outlined font used in 65-68). The later ones do not have that.
Version E. Same as the later Version D filters, except they eliminated "BEST WAY", and the silk screen starts with "PROTECT YOUR ENGINE ..."
The earliest box with one of these I have seen had no date but included 1975 model year vehicles in the list of applications on the box. So elimination of the BEST WAY apparently occurred some time between 11/1974 and approximately 8/1975 (when 1976 models came out and the boxes would have included 1976 models if the filter had been made after that).
And I have examples of Version E going all the way up to boxes dated 3/1977.
Version F. This is the "expanded metal" mesh, that looks like a chain link fence (what most people call "Diamond Mesh"). And it has silk screen starting with PROTECT YOUR ENGINE ...
The earliest box with an A212CW diamond mesh filter I have seen had no date but included 1979 model year vehicles in the list of applications on the box. So it was made, at the earliest, in approximately August of 1978. But see **footnote below.
And I have examples of Version F going all the way up to boxes dated 5/8/1986.
Version G. Same as Version F , except they eliminated the PROTECT YOUR ENGINE ... silk screening.
**Footnote re diamond mesh filters -- Although I have never seen a diamond mesh A212CW in a box dated earlier than 1979, I have seen other AC filter numbers with diamond mesh screen in earlier boxes. The earliest one I have saved was a cowl plenum filter in a box dated 8/4/1976. Notably, it was in a plain GM service parts box with just an AC sticker with the part number on it (like you would have gotten at a dealership), and not the commonly seen AC Air Filter box like you would get at a NAPA store.
So the diamond mesh material was in use by AC on some filters before they stopped making the square mesh 212's some time after March 1977. But the question is whether the diamond mesh was also being used to make 212's at the same time square mesh 212's were still being made.
I know there are pics on some forums of some 69's that are supposed to be from soon after the cars were new, that have diamond mesh filters. But anybody with a car with a diamond mesh filter that they think is original needs to check the silk screening. If it is diamond mesh with "PROTECT YOUR ENGINE" silk screening without the "BEST WAY", then the filter was made after 1974. If it is diamond mesh with no silk screening, then the filter was made some time after May 1986.
And beware, there are some people who have recently started selling later 212 filters on ebay that they are adding the silk screening to in order to jack up the prices. On some they are taking original "PROTECT YOUR ENGINE" filters and adding the "BEST WAY", because you can see that the "BEST WAY" is not in line with the rest of the stamp and the ink looks a little different. On others, they are adding the entire stamp. So there is no longer any way to rely on what you see listed on ebay.
