I would like to take screenshots of my Macintosh Classic with system 7.0.1 and then open the images in a PC to, for instance, use them in a blog.

I know there was a keyboard combination that I don't remember now, but the image file created had no extension (simply was «Screen01» with no .gif, .jpg, .bmp, .tif.....nothing) and I found no way to open it in a Linux or Window$ box...by means of GiMP, Photoshop....they didn't love the file. :-/

How is this accomplished?

By now the only screenshots I take are like this....