The Last 5 Digits
By Bill Smith

How many times have we looked
at the steering head tube on a CMF (Chrome Moly Frame)
Penton motorcycle and wondered what do all these numbers
mean? First let's address the two types of frame numbers.
The first type consists of 8 digits. This type pertains
mainly to the Sachs powered models though I have found KTM
powered models using this as well. As stated in several past
newsletter articles and the website Production Year Guide,
the first digit represents the year (i.e. 2 = 1972) and the
next two digits represent the month (i.e. 05 = May). For
example, if the frame number were 20555144, this would be a
model built in May 1972, with the remaining digits being the
actual serial number.
The second type consists of the same 8 digits but also has
an extra 7, 51, or 54 ahead of the original 8 digits.
These extra digits could be called production codes for the
lack of anything else to call them. These digits were only
found on the KTM powered models. If the 7 appears, you are
looking at an allnew Jackpiner model starting with June
1972 through June 1973. The 51 and 54 seem to start where
the 7 number ends which is June 1973 through September
1976. This period was the time when the rear conical hub
first appeared and numerous design changes started. To find
the year, month, and serial number, you simply disregard the
7, 51 or 54 and look solely at the last 8 digits. For
example, 720655454 would be a model built in June 1972,
with the remaining digits again being the actual serial
number. In some cases, frames have been found with no frame
numbers stamped in them at all. It is believed this type of
frame was most likely a replacement frame.
With the production code, year and month being addressed,
what is left? The last five digits. In the past, I would
always look at a set of frame numbers and say to others, or
myself the 7, 51 or 54 didn't mean too much. The next 3
digits are year and month, and the last five digits are
"just the serial number." I never realized how important the
last five digits were until a few months ago. The last five
digits are the whole key to total production to all Penton/KTM
models. Not only is it the key to total production but the
year and month production as well when using the year and
month part of the frame number. And it's even the key to who
has the earliest or latest CMF 100cc, 125cc, 175cc, 250cc
and 400cc models. Remember the talk about the steel tanker
models and V001 being the very first Penton every produced
and how everyone was trying to find steel tankers with the
lowest "V" serial number possible? Now that holds true with
the CMF models as well. How do I know this? After compiling
over 200 frame numbers, I put them in ascending order by
using just the last 5 digits of the serial number, and to my
surprise, the year and month part of the frame number
automatically ascended in perfect order as well. What was so
interesting about this was that the serial numbers never
quit climbing from June 1971 to September 1976. Another
interesting note was that in one or two cases the year or
month seemed out of order and did not follow the expected
pattern. In these cases, it showed that the frame number
given to me was an error, whether it was the year, month or
the 5digit serial number. And in every instance, an error
was found and corrected.
What this list has shown me to date is that the earliest
frame number I have recorded is 10650190. So we know now
that CMF production started in June 1971. If the 5digit
serial number started with 50000, this would be the 190th
unit ever produced. If the 5 digit serial number sequence
started with 00000, this would be the 50,190 unit produced,
and that sounds almost impossible. So guessing, I would say
that the base serial number was 50000. The highest number I
have recorded is a 5460993213. So if you subtract 50,190
from 93,213, this puts total production from June 1971 to
September 1976 at 43,023.
In 1976 a new frame number appeared on the allnew MC5,
125cc through 400cc models. These numbers started with
550xxxxx and seemed to stay with these first three digits
for the next two years, 197677. Once again, I put the last
five digits in ascending order and it appeared the serial
numbers originally started with 00000. The earliest 550
frame number I have recorded is 55000865 which tends to make
me believe that this was the 865th MC5 ever produced since
1976.
In 1977 another new frame number appeared on the allnew GS6
125cc  400cc models. These numbers started with 701xxxxx.
The earliest GS6 frame number I have recorded is 70100047.
Once again, I tend to believe that this is the 47th GS6
model made from the start of production if starting with the
00000 again. Note: I have come across a 70201375 and a
70301662 frame number but have no other data on these
numbers. Nor do I know when the first 3 numbers might have
changed to a 702 to a 703.
After working with these frame numbers, I thought it might
be fun to do some research into KTM engine numbers. With
some 75 engine numbers to work with, I separated them into 3
categories: Type 52 which is the 175cc, Type 54 which is the
250cc and Type 55 which is the 400cc. However, I did not
have any Type 51 125cc numbers available. What I learned was
that putting each type in ascending serial number order
showed that each size engine serial number started back at
00000 and went forward, unlike the frame numbers and all its
models that ran consecutively year after year. And again,
the year part of the engine number automatically ascended in
perfect order as well. The lowest Type 52 number that I
recorded was 25200566 (manufactured in 1972). The lowest
Type 54 that I recorded was 35400341 (manufactured in
1973). And the lowest Type 55 was 45500164 (manufactured in
1974). This makes it seem very logical that you could
actually have 2 different size engines with the same serial
number.
In conclusion, the above information could be a very
powerful tool to uncover the true history of production
during the Penton/KTM timeline. I'm sure production didn't
stay even year after year with models changing or swings in
the economy. With the ability to find yearly and monthly
production or who has the earliest or latest of any given
model, the only thing we need is your input. If you even
have a junk frame or two, like so many of us do, this could
be the key to something down the road. It would also be
great if we could receive European KTM frame numbers as well
as any Penton frame number sold as KTM's on the west coast
from 1975 on. I believe these models will have the same
ongoing numbering system as that of the Penton and help shed
even more light on the subject.
Below you will find hyperlinks to a Frame Number List and a
Engine Number List. These lists are comprised of numbers
that I found on the old Bike Registry, those given to me by
friends and some found on the POG message board. In any
case, I hope this allows you to enjoy our passion with even
more interest and enthusiasm than ever before. If you do
have numbers and would like them to be included on this list
(your name will be kept confidential and not appear on the
list), please email the information to
Penton Owners Group. Be sure to include the
full frame number and engine size if known. If you want to
send your engine information, be sure to include the full
engine number. 

