Why can HTTP headers of the same image differ on different computers?

Question

Images

I go to the same site that has a png image from my home and work computer.
When booting from home (also on a virtual machine), the answer comes:

HTTP/1.1 200 OK
Content-Type: image/gif
Cache-Control: max-age=300
Content-Length: 43

When booting from a worker and any others (and from a laptop on the same wire as the home computer):

HTTP/1.1 200 OK
Date: Wed, 15 Feb 2017 10:10:57 GMT
Server: Apache
Last-Modified: Sun, 18 Dec 2016 10:48:05 GMT
Accept-Ranges: bytes
Content-Length: 2981
Cache-Control: max-age=2592000, public
Expires: Fri, 17 Mar 2017 10:10:57 GMT
Keep-Alive: timeout=5, max=98
Connection: Keep-Alive
Content-Type: image/png

Other pictures are displayed correctly. What could be causing this strange behavior?