Help me ID these mecha cels

Hi there,
Can anyone ID what anime these cels are from? I got them in a lot purchase years ago; I wrote down their series title, but I lost the note.
I do recall that these 3 were from the same series (the seller ID'ed them that way anyhow). Here is the image link:
https://imgur.com/a/Fr6b88w

If you have any trouble viewing that link, just let me know. I can use a different image host if needed.

I would greatly appreciate some help with this! Thanks!!!

Tetsujin 28-gou FX, the number kinda give it away

Thanks a lot! I don't know my mechas very well, so this was a big help.
Much appreciated!