I went with text/vnd.simoncozens.fez but I think a real one should be defined
[fred@デブ.狸.agency ~]$ curl -I https://ftp.mfek.org/FRBAmericanCursive/fea/classes.fez
HTTP/1.1 200 OK
Server: nginx/1.25.2
Date: Fri, 22 Sep 2023 14:53:28 GMT
Content-Type: text/vnd.simoncozens.fez
Content-Length: 3048
Last-Modified: Sat, 15 Apr 2023 07:06:05 GMT
Connection: keep-alive
ETag: "643a4cdd-be8"
X-Clacks-Overhead: GNU Terry Pratchett
X-Clacks-Overhead: GNU Natalie Portman
X-Clacks-Overhead: GNU Stephen Hawking
X-Clacks-Overhead: GNU Leonard Nimoy
X-Clacks-Overhead: GNU Terry A. Davis
X-Clacks-Overhead: GNU Aaron Swartz
X-Clacks-Overhead: GNU John Perry Barlow
X-Clacks-Overhead: GNU Douglas Adams
Accept-Ranges: bytes
I went with
text/vnd.simoncozens.fez
but I think a real one should be defined