Why are there 3 2.9.2 ISO files?

There's this one:
linuxcnc.org/iso/LinuxCNC_2.9.2-amd64.hybrid.iso

And this one:
linuxcnc.org/iso/linuxcnc_2.9.2-amd.hybrid.iso

And this one too:
linuxcnc.org/iso/linuxcnc_2.9.2-amd.hybrid.iso

On my mirror, www3.langdonstaab.ca/iso, I would like to remove these likely duplicates to reduce bandwidth and load for my server in the event that someone downloads all the files on my server (with wget -r or something).

Are these files identical?

Why are they still there?

Which one is actually correct?