Cycles Peugeot attached aluminum labels to some of its frames from 1972 to 1978. From 1972 to early 1976 the bicycle serial number was stamped into the metal label.

The labels were a metal strip riveted to the bottom bracket. The labels had numbers only stamped into them.

From 1972 and into early 1976 the number on the aluminum label was a serial number
which also served as the frame number. As far as I know there where no other labels on these frames with serial numbers. The bicycles with metal labels had no other frame numbers stamped into the dropouts. Some of the frames made at Romilly did have a date code stamped into the bottom bracket.

In 1976 Cycles Peugeot changed the way in which they placed the serial number on the frame.
I would like to explain the distinction that I have made about this change. In 1976 there became two distinct things on many Peugeot frames: the serial number and the frame number.

In this post I am concerned with the aluminum labels up to 1976, before the switch to the date coded frame number labels.

On these metal labels I have seen one two digit number, one four digit number, and several 6 digit numbers. However the vast majority of numbers are seven digit.

Note: The two digit and four digit numbers. I think these are not original numbers, but later over-struck numbers on a filed down aluminum strip.

Of the seven digit numbers, the range of leading digits include only 0, 1, and 2.
(The leading digit of the aluminum labels with date encoding is a different range of numbers.)

The question that I try to resolve is: Are the serial numbers sequential from 1972 to early 1976? By sequential I mean the numerically smaller numbers are 1972 and the numerically larger numbers are 1975 and 1976.

The answer I would say is: No.

However there may be some sort of sequencing occurring.
Possibly within a year.
Possibly within a factory.
Possibly within a range of models.

More data needs to be collected and detailed analysis of that data is needed.