On 13 Sep 2021 Vietnam issued a set of four stamps to honor historical figures. This stamp shows an island, probably in the South China Sea. It may not be a true representation of an actual island and the lighthouse shown is unidentified. If you have any ideas, please post a comment below.
![Unknown L/H | 13 Sep 2021 Unknown L/H | 13 Sep 2021](http://lighthousestampsociety.org/wp/stamps-viet-nam/cache/vie32021s01.jpg-nggid0512111-ngg0dyn-230x230x100-00f0w010c010r110f110r010t010.jpg)
Thanks to Jaap for finding this stamp.
See more lighthouse stamps from Vietnam here