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Centurion serial number decoding

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Centurion serial number decoding

Old 10-08-17, 10:52 PM
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Centurion serial number decoding

Originally Posted by T-Mar View Post
The following represents the current understanding of the various serial number formats used on Centurion models marketed by Western States Imports in the USA. Serial numbers were statistically analysed and the results compared against component date codes and extant literature.

1980-1990 Japanese models:

Most Japanese models during this period use a serial number format WXYZZZZ where;

W = a letter, purpose uncertain, but probably indicates manufacturer or Centurion
X = a number, indicating the calendar year of manufacture
Y = a letter, indicating the fortnight of manufacture (A = wk 1 & 2, B = wk 3 & 4, etc)
ZZZZ = four digit number, probably indicating frame number during fortnight

Example: N4E0283 indicates the 283 frame manufactured during the period of weeks 9-10, for the year 1984.

The letter prefix for these codes is typically 'N'. It has been suggested that this represents National, the Japanese market brand for Panasonic, which are built my Matsu****a. While the Panasonic branded models use a similar format, there is no prefix letter, nor is there a letter prefix on the Matsu****a manufactured Schwinns. This suggests the N-codes are be another manufacturer. reportedly Tano, though this is unconfirmed.

However, a number of circa 1984-1985 Centurion have turned up that match the Matsu****a format.


Miki manufactured models (circa 1975-1980)

During the late 1970s, Japan based Miki appears to have manufactured the upper end Centurion models for Western States Imports;

Serial number format Myfxxxxx, where,

M = Miki
y = number indicating year of manufacture
f = letter indicating fortnight of manufacture (i.e A = weel 1-2, B = weeks 3-4,,,,Z = weeks 51-52)
xxxxx = sequential frame number within the fortnight

Example: M7C11265 is the 11,265th frame manufactured by Miki during the 3rd fortnight of 1977.


. . .
This quote: Last edited by T-Mar; 05-03-17 at 04:51 PM.

The Centurion serial numbers with the fornmat Nytxxxx,

where N = "N" frame manufacturer designation of a Japanese frame manufacturer.
y = digit, last digit in the year
t = alpha character for the manufacture time frame within the year.

It has been often stated that "t", time frame, alpha character indicates fortnight within the year.

This "fortnight" time frame never seemed right to me, as this is for a Japanese manufacturer.

For this manufacturer, where did this fortnight idea come from? I have seen no documentation to corroborate the time frame as fortnight.

This serial number format for Centurion is found from 1978 to 1989, 12 years. I have done a year by year analysis of the third character, the time frame character, for this serial number format.

The analysis shows that of the 26 letters of the alphabet, only 15 letters have been reported in serial numbers.
If the time frame is fortnight, i think you can expect that more than 15 letters would be used.

Of these 15 letters, three letters where only reported once in the 12 year history.
If you exclude these, then there are twelve letters.
All the other 12 letters were reported at least 15 time each, over the 12 years of serial numbers.

Twelve letters for twelve months?
Here is how the letters would decode as months:

A = January
B = February
D = March
E = April
G = May
H = June
K = July
L = August
M = September
N = October
P = November
S = December

This letter/month decoding is exactly the same as TI Raleigh serial numbers from 1973 to 1989.

The three letters with one reported occurance: "C", "F", "O".

This analysis is for 275 serial numbers over the 12 years, an average of almost 2 serial numbers per month.

Over the 12 years "P" is the most common letter found, November. November seems like a good time to manufacture frames to be in place for the start of the next year bicycle season.

The analysis does not include "N" serial numbers from Centurian Australia, Diamondback mountain bikes, or any of several other brand names that had frames with serial numbers with the same format. However serial numbers that I have seen from these sources have no exceptions to the month time frame letters that I have listed above.

* * * *

A similar analysis of Miki serial numbers will reveal that the third character of the serial number for time of year of manufacture is unlikly to be fortnight.

More likely to be monthly, but using a different subset of letters for month than listed above.

A = January
B = February
C = March
D = April
E = May
F = June
G = July
H = August
J = September
K = October
L = November
M = December
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Old 10-09-17, 11:23 AM
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An interesting and meritorious analysis. However, it's impossible to say if codes 13-15 are true codes or just cases of erroneous reporting or factory errors. Certainly, it is a possibility that I wouldn't rule out.

In the case of Miki, I have seen codes beyond those mentioned but again, there is not the distribution you would expect.

Another possibility which I have often considered, is the probability of a 13 letter system. This divides a year into equal segments of 4 weeks and is known to be used by some manufacturers.

The fortnight system is not unknown to Japanese manufacturers. Miyata immediately comes to mind, having introduced what appears to be a fortnight system at the beginning of the 1985 model year. A number of different of different manufacturers have changed formats, which often makes analysis difficult.

I have always stated that my serial number analyses are dynamic in nature and based on current understanding of the data. New data may change views. The more data that is collected, the higher the confidence level. However, they are only educated guesses based on data analysis. The only way to know for sure if an analysis is correct, is via extant manufacturer literature. Unfortunately, there are very few cases of this.
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Old 10-10-17, 09:48 PM
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Originally Posted by T-Mar View Post
An interesting and meritorious analysis. However, it's impossible to say if codes 13-15 are true codes or just cases of erroneous reporting or factory errors. Certainly, it is a possibility that I wouldn't rule out.
I am not sure what point you are trying to make here.

If you are talking about the 3 excluded serial numbers, none of the three had a picture of the serial number. All were entered by hand. One of the serial numbers was only six characters long, when it should be seven characters, so it was incorrectly entered on at least one count.

Three serial numbers entered incorrectly out of 275 is little more than a 1% error rate. Having worked in the IT industry for many years I can tell you that 1% error rate on data entered at a key board by non-professional typists is low.

In reading this forum I regualarly notice that members enter serial numbers incorrectly. When I see this, I sometimes politely ask the member to check the serial number again. In almost all cases when the member reports back they indicate that they misread the serial number on the bicycle or they mistyped the serial number.


Originally Posted by T-Mar View Post
In the case of Miki, I have seen codes beyond those mentioned but again, there is not the distribution you would expect.
On the Miki serial numbers I would be interested to see several examples with letters for the time of year outside the range listed, with pictures of the serial number and the brand name and model. Somehow I seem to have missed these in this forum, which is quite possible because I do not read every thread or post.

Originally Posted by T-Mar View Post
The fortnight system is not unknown to Japanese manufacturers. Miyata immediately comes to mind, having introduced what appears to be a fortnight system at the beginning of the 1985 model year. A number of different of different manufacturers have changed formats, which often makes analysis difficult.
What happened at Miyata has nothing to do with Centurion serial numbers.

Yes, many manufacturers have changed their serial number format from time to time. What does that have to do with the limited area of Centurion serial numbers that I described?
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