Generally when you are getting samples from China vendors for a new product there are three samples you want to be concerned with. Sometimes people confuse these terms so I thought I would clarify them.
Proto samples. are samples of a product where the design has not yet been fixed. For example I currently have a customer who has a concept for a new product. I gave some specs to a vendor in China whom I have worked with before and the vendor did some samples for me. The samples are rough but they will give my customer something to build on. Sometimes it may take two or three rounds of proto samples to get a sample and product you are pleased with.
Pre-Production samples. Once you have approved a product or design, you request samples from the vendor for approval. These are Pre-Production samples and should mimic production. However, from my experience, even pre-production samples sometimes need a couple of rounds before the vendor gets it right. Ideally you want the vendor to submit multiple pre-production samples to you so you will have plenty in the event you send someone to China to do an inspection or if go yourself (advisable). You also send some of the approved samples back to the vendor with a date and signature so they will have a standard for production. Some vendors are very sloppy about keeping counter samples so you need to discuss this with them and insist on it. Just remember it is always better to be stuck with too many samples than too few.
TOP or production samples. Assuming you are not in China for the production and your vendor is proceeding on his/her own, you need to ask your vendor to send you samples from the first lot of production This will allow you to see that everything is going as per the approved samples ( you would be surprised how often it doesn’t ) Ideally you would want the vendor to stop production until you have approved TOP samples, but of course most vendors are not willing to do this, especially if they have other orders to do. Still insist on the TOP samples, have your vendor FEDEX them to you and let them know if anything is remiss ASAP. You might even draw it into your sales contract that TOP samples must be sent and approved before the bulk of production can be started. Depending on the vendor and how badly they wanted your business, they might agree to this.
A final thought: Always have your vendor label your samples clearly and preferably in marker and not with a tag. Tags fall off. Ink does not. Anyone who has dealt with as many samples as I have knows how easily samples can be mixed up, misplaced, lost, or simply mis-tagged. The best way to prevent this is with a marker.