Portal (1986) by Activision Publishing, Inc.
Sold at CDaccess:
http://www.cdaccess.com/html/pc/vault3.htm
Sorry, I'm quite sure there's something wrong with cd access, but I can't approve your game until we won't discover it.
Same link but here you can see the stock:
http://www.cdaccess.com/html/quick/vault3pr.htm