Nameplate ratings on labels often throw people off because manufacturers may not provide context and even have “missing” information. Some labels require very specific information or it could fall out of compliance. Other labels may not be governed by strict regulatory standards and follow internal manufacturer conventions. If something is missing on a label, don’t always assume that the datasheet is incorrect.
Example Part 2603-CI35P-28E210-C-1X-ND (CI35P-28E210-C-1X)
The label on this buzzer seems to be missing some information, the AC voltage rating. The datasheet does show what it looks like on the label, see below.
The label clearly says it works with a voltage range of 6-28VDC, but where is the AC rating? The answer is that the label may not always dictate all specifications. Datasheets always take precedence for specifications. See the snippet from the datasheet below.
Why is this not printed on the label? My most simple assumption is that there wasn’t room for it. The original customer who asked confirmed that the part does indeed work with the appropriate AC voltage range.
More About Labels - Standards
In many cases, nameplate content is driven by certification requirements (UL, CE, IEC. etc.) which often require a specific set of markings/information. They aren’t intended to communicate an exhaustive electrical compatibility. If a rating is not required for safety certification, manufacturers may omit it to conserve space or simplify their labels.
Conclusion
A missing rating on a nameplate should be treated as incomplete information, not contradictory information. The datasheet remains the governing document for electrical compatibility.
Related Topic
I wrote a related topic about perceived “conflicting ratings” on sensing equipment:
This post can add further context about labeling practices if you have further questions.