Guitars and basses prior to 1970 did not have serial numbers.
1970 was the first year, and the serial number sequence began with 5000 (versus something like 0001).
Unlike most other manufacturers' serial numbers, there are no hidden "codes" in a Carvin serial number that indicate year or month of production, or anything else. Carvin serial numbers can be located in several different places.
Click the picture to see the entire Hfner advertisement.
Due to the amount of customization available on Carvin guitars, identifying the specific model can sometimes be difficult.
One of the first general giveaways to the year of a particular model is the logo on the headstock.
This will at least identify if it's pre- or post-1988, which was the year that Carvin switched from the curved logo to the block italic logo.
Carvin guitars and basses from 1964 until 1978 had bolt on Hfner necks, and the SH225 was made by Hfner and sold under the Carvin name.
The headstock on the left is from a late 80's Hfner Nightingale. Although the headstock shapes are different, there is no mistaking the inlay in the center.
The chart below will help narrow down the year of production based on certain general features.
Not all features are options are listed here; this is just a quick-reference guide.
Serial numbers can be of some help in narrowing down the possible guitar models available for any given year, but the most accurate method of making the determination, particularly on a guitar where the serial number is not known, is by looking at the woods, hardware, and headstock, and then seeing what models from what year fit that criteria.