pcap-savefile(5) on FreeBSD
The text 16f5baa11bc8, as FreeBSD 13.4-RELEASE, FreeBSD 13.3-RELEASE, FreeBSD 13.2-RELEASE, FreeBSD 13.1-RELEASE, FreeBSD 13.0-RELEASE, FreeBSD 12.4-RELEASE, FreeBSD 12.3-RELEASE, FreeBSD 12.2-RELEASE, FreeBSD 11.4-RELEASE shipped it.
libpcap savefile format