Before the trademark registrant applies for trademark registration, if another person has used a trademark that is the same as or similar to the registered trademark and has a certain influence before the trademark registrant, the exclusive right to use the registered trademark has no right to prohibit the user from continuing to use the trademark within the original scope of use, but he may require it to attach appropriate distinctive marks.
It can be seen that a prerequisite for applying the defense of prior use of trademarks is "certain influence". As for how high the requirement of "certain influence" is, it is not mentioned in the trademark law and related judicial interpretations. In practice, including trademark review and adjudication board, intellectual property court and civil tort disputes, the standards adopted are mostly based on the length of trademark use, the size of geographical coverage, the size of use scale, and even the subjective attitude of early users.
Personally, although there is no restriction on "certain influence" in laws and regulations, it should not be based on "certain influence" nationwide, but should be judged according to specific cases. Generally speaking, it only needs to have a "certain influence" within the geographical scope or industry scope of the previous user. Of course, if it appears in a trademark infringement dispute, the first user needs to take the initiative to prove it.