[jeffschevelle]

The technical term for the screen in the pic above referred to as "Diamond mesh" is "expanded metal" mesh. The square version (both horizontal/vertical and diagonal) I refer to as "soldered wire" mesh; and for shorthand I call the horizontal/vertical version "square soldered mesh" and the diagonal version "diagonal soldered mesh".

Ignoring the expanded metal ("diamond mesh") filters, the progression for the soldered mesh filters that I have determined from original A212CW filters in their original cars, and from the dates on service replacement boxes for A212CW's and A212CX's (the heavy duty version with an extra layer of the inside mesh behind the outer mesh), is:

- 1965 through approx 2/1968 - Diagonal soldered mesh, no white print, filter number is embossed on the black rubber in large outlined letters.

- 3/1968 - same as above, except the white "BEST WAY TO PROTECT YOUR ENGINE" stamp is added. This pins down pretty good when the white print started, because they had stock with the embossed rubber still on hand that they stamped. Later does not have the large outlined embossing.

- By at least 12/05/1968 - Diagonal soldered mesh with white "BEST WAY TO PROTECT YOUR ENGINE" stamp. Large outlined embossing eliminated. Continues through at least 7/14/1969.

- In box showing 1970 model year as highest year (so could have been made any time between 9/1969 and 8/1970) -- Square (horizontal/vertical) soldered mesh, with white "BEST WAY TO PROTECT YOUR ENGINE" stamp.

- 1972 model year box -- Square soldered mesh, with white "BEST WAY TO PROTECT YOUR ENGINE" stamp.

- Boxes dated from 3/1973 - 11/12/1974 -- Square soldered mesh, with white "BEST WAY TO PROTECT YOUR ENGINE" stamp.

- In box showing 1975 model year as highest year (so could have been made any time between 9/1974 and 8/1975) -- Square soldered mesh, with white "PROTECT YOUR ENGINE" stamp. The "BEST WAY TO" part of the stamp was eliminated. (I would not be surprised if the FTC threatened action for using "best way" in their marketing, without proof that it was demonstrably the best available filter on the market.)

- Boxes dated from 1975 model year - 3/1977 -- Square soldered mesh, with white "PROTECT YOUR ENGINE" stamp.

- Everything after that is the expanded metal ("diamond") mesh. The "PROTECT YOUR ENGINE" stamp continued until at least 5/8/1986. Later filters have just the A212CW stamp.

*************
As to production of the expanded metal (diamond) mesh filters BEFORE 1977, there are a couple pictures of alleged original filters in 1969 Camaro's out there. Unfortunately none of them show which version of the white print they have on them. (I do note that the fantastic low mileage black 69 L78 at MCACN last year had an original diagonal soldered mesh filter in it.)

As far as dated service replacement boxes go, I have recorded the following for the expanded metal filters:

- 2/16/1970 and 5/1970 dated boxes - A212CW with expanded metal mesh, with white "BEST WAY TO PROTECT YOUR ENGINE" stamp.

- 3/1970 and 1970 (no month) dated boxes - A212CX with expanded metal mesh, with white "BEST WAY TO PROTECT YOUR ENGINE" stamp.

- 8/4/1976 and 8/19/1976 - A226CW (cowl plenum) with expanded metal mesh, with white "PROTECT YOUR ENGINE" stamp. (No "best way")

- Boxes dated from 1979 model year through 5/8/1986 - A212CW with expanded metal mesh, with white "PROTECT YOUR ENGINE" stamp.

Cheers!