67 Vent glass codes. M74 vs M75
My 67 Coupe has the left vent glass marked as M74, the right side is marked M75. The dates are left GZ - April and right LZ -March. Both are tinted and appear to be the same thickness and are marked the same other than the dates and these M codes. The Judging Guide call out the vent glass as M74. Any idea what the M74 and M75 mean? AOS Body built June 7th. Thanks
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In three different postings on the Corvette Forum Huntforcleanair said:
All glass has three codes; a date code, a specific "M?" glass type code and an AS1 (or 2) code...all are standardized following the American National Standards Institute standards. The AS2 indicates laminated glass (side window specific)...AS1 windshield. Later in 78, we see AS3 for laminated glass t-tops! C3 coupe glass used an M74 glass while convertibles displayed an M75 code. Astro glass was produced for either body style with either the M74 or M75 glass.
And than there is the "window type" code so coupe windshields will carry an M24 code while side glass would call for either M74 (coupe) or M75 (convertible).
M74 Corvette coupe side window
M75 Corvette convertible side window
You might contact that Corvette Forum person and see if he can answer your question.
Gary -
Re: 67 Vent glass codes. M74 vs M75
Gary,
Thanks for the info. I think I know who that is, I'll reach out to him.
KurtComment
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Re: 67 Vent glass codes. M74 vs M75
Gary,
There is a group of us working on the 78/79 revised Judging Guide and the M Codes are mentioned in there as Coupe and Convertible. I sent a note to Tom Russo, he may know more.Comment
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Re: 67 Vent glass codes. M74 vs M75
M Codes! Drive me nuts as coding expanding by the late 70s. But lets remember that with Astro-Ventilation (C3), side windows are gone! But the AS3 designation, used on Glass T-tops is defined as "American Standard code forprivacy glass with a darker tint. AS3 indicates no more than 70% of incominglight can pass through; used in rear side glass."
Interesting enough in 1978 with that large, expansive rear window, we get an M81 code when the rear window has the electric defogger element. Otherwise, it reverts to the M74 non-heated, designated AS2 same as side window glass.
Having studied 74 and up glass codes, they remained rather stable. Here's what is in the draft for the 78/79 timjg:
Side WindowsAll glass is LOF Safety Flo-Lite, Soft-Ray tinted, solid tempered, and designated AS-2. The M74 safety code designates a Corvette side window. The date code is not in a depression, as is typically found on reproduction glass. Judges may have to stand back four or five feet from the window and view reflections of straight lines to see the depression. Original glass is thicker than some reproductions. Replacement glass has a subtle waffle pattern that is often visible, especially when viewed through polarized glasses.
Rear Window
A new rear window glass design was introduced in 1978, incorporating a “fastback” style, a throwback to the ever-popular C2 model, designated AS-2, the same as side glass. The glass is also LOF, Safety Flo-Lite, Soft-Ray tinted. The two-letter date code is located on the passenger’s side forward corner of the glass. When equipped with C49 defogger, M81 is the rear window glass code; M74 is non-C49 glass. (Fig. E 11.1)Tom Russo
78 SA NCRS 5 Star Bowtie78 Pace Car L82 M2100 MY/TR/ConvComment
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Re: 67 Vent glass codes. M74 vs M75
FWIW>Picture below is the P.S. Vent Glass(Non Tinted) that I took out of my 66
Convertible this Summer. Replaced it with the proper date code and "Soft Ray" Glass.
Not sure what this M code means. Comments? Thanks>LarryLarry
LT1 in a 1LE -- One of 134Comment
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