Is there a decoder ring for the numbers stamped on the rivets of the lower control arms? The numbers are three digits such as 811 and 268 on a B body control arm. The numbers don't appear to be week and year or day of year. Anyone know what the numbers mean?

From my 1970 Valiant;

Lower control arms 021 069 (1970, second shift, line one) & 69th day of 1970 = March 10th, 1970

So it is two different codes? They both have the year in the first digit but then the day on one rivet and line info on the other rivet? That doesn't seem to work with the codes on this control arm.

The arm pictured above could be from 1968 since it has the anti-sway bar tab on the outside, but that would mean that 811 is 1968 and the 11 is something else. While the 268 would be 26 means something and then 8 is for '68. But that is backwards from TA's example.

From TA’s example, wouldn’t your’s be: 1968, first shift, line 1; and 268th day of 1968?
Bob

811 decodes as:
8: 1968
1: first shift
1: first line

268 decodes as:268th day of 1968 (Sept 24th)

268 is the day in the year that the LCA was put together.
268th day in 1968 for a early 69 build automobile.
The first digit 8 on the other rivet head is the year, the other digit's are the assembly line that it was manufactured on, and the shift that it was put together.
But i forget which of the two, are which, without looking it up.
Pretty much meaning less anyway, in code deciphering.

811 - 1968 First shift, line 1.

268 - 26th day of 1968.

IF what I was told when I asked here long ago is correct?

(I have not looked at enough of these to know if the date code on the 2nd rivet ever went into 4 digits.)

268 is the 268th day - not the 26th day of 1968. (The 26th day would be a 1967 model)

Okay got it. One rivet has the day of the year starting at 001 while the other one is the last digit of the year and then line and shift info. That makes sense for all of the ones I have on the shelf. And the year is the year of mfg not the model year. So anything past roughly day 180 will be the next model year.

Oh, I forgot to mention that I have a set of B body control arms where the rivet heads are blank. Not sure what that means. Over the counter parts? Still seems like the mfg would mark them all since I doubt the mfg knew where they were going. Could be a missing stamp or perhaps someone sanded them smooth for some weird reason.

OK, That makes more sense than what I said, thanks!

The plant that manufactured the LCA's didn't start stamping them with codes until the end of the 1960's sometime.
So finding earlier ones without stampings is perfectly normal.

Okay, that makes sense. The set I have without any mfg stamps are from a B body car with the outboard LCA tabs. So they could be as early as a '66 model with mid-65 production date.

I snapped a picture of a '70 LCA with the mid-mount LCA tab. Looks like this LCA was put together on the 237th day of 1969 which would put it into the beginning of the '70 model year. Thanks everyone for the help.

I have had this graphic saved for years - it's accurate at least as far as the 1970 Challenger I own. The second photo is one of the LCAs from my car, an R/T SE with spd of 109 (1970). Though not a b-body, it seems to support the three digit meanings.