What does this traffic sign indicate?

You correctly identified this traffic sign as indicating a customs point.

This sign means that you are approaching a customs checkpoint where vehicles may be stopped for inspection by customs authorities. It is important to be prepared to slow down or stop and follow any instructions given by officials. This sign is used at border crossings where customs control is in force.

It is not a toll road sign, which usually indicates a road where fees must be paid for use, nor does it prohibit through-traffic. Instead, it signals a legal requirement to comply with customs regulations and controls at this point. Understanding this helps you know when to expect inspections and be ready to cooperate with customs checks during your drive.