I have been making leather goods 10 for many years, and it is very simple to remove bronzing (including imprint). The following is definitely not copied from any internet, but my 10 years of work experience:

1. White electric oil (basically available in chemical stores), drained with cotton cloth or gauze; Wipe it and it's gone. It's simple.

2. If there are obvious marks: cover them with thin gauze and scald them several times.