Check Gunnar's FAQ.
Where do I find my serial number? Why is the serial number so important?
The serial number is always found on the bottom of the bottom bracket shell. You can find it on the parallel to the non-drive side edge, as shown below:
For purposes of entering your registering your bike, the space between the letters and the numbers are ignored. The example above would be recorded as H08002. Every Gunnar gets a serial number - even team and employee bikes. It is not unusual for numbers to be partially obscured by paint. If you are the original owner, your dealer should give you the serial number when you buy your Gunnar.
For used Gunnar buyers, we recommend that you get the serial number before you buy, especially if you want to ask us questions about the frame. If you have a description of the frame (including model, size, color, original owner name and/or dealer name), we can help you get the correct serial number even from a limited number of letters.
When you register your Gunnar, we use the serial number to connect you to the original order, so as to create accurate provenance records for the frame. We also include the ability to document any alleged theft of your Gunnar (though we do not report thefts to any authorities at this time).
Because every Gunnar has a serial number, you should be suspicious if your Gunnar does not have one, or if, when shopping, your seller cannot provide you with a serial number.
And
What does my Gunnar serial number mean?
A Gunnar serial number not only uniquely identifies a Gunnar, it also tells you the date of manufacture. Each serial number consists of three components:
Letter indicating the month: The serial number starts with a letter indicating the month of manufacture, with A for January, B for February and so on. Gunnar skips I, which can be confused with a 1, so September becoms J, October K and December M.
2-digit year code: The next two digits are the year - 08 is for 2008, for example.
3-digit sequence number: This number is assigned as the serial numbers are allocated, which is the first step in fabrication.
In the example below, H08002 means the frame was the second sequence number allocated for August, 2008 production: