The Alan Class web-site says only 8 issues were published but I have issues #9 and #10!
This title came out in the same year as the one-off Race into Space and Space Adventures Presents Space Trip to the Moon.
Interesting that these science fiction try-outs didn't quite catch on as well as the horror/mystery anthologies that began with Creepy Worlds.
Note: some PR issues may have no value. Selected issues in FN, VF or VF/NM may not exist in some titles.