Common practice. When I was involved in doing RFPs for hardware, you were allowed to say "We need a computer. It needs to be 32 bit. It needs to have such-and-such amount of memory, be able to run Unix, and ..." You could even say what color it had to be.
Then they'd print a bunch of copies of these several hundred page documents up and mail them to IBM, Honeywell, Wang, DG and DEC and so forth for bids.
The guy at (say) DG would get this, see that the Govt wanted a Vax, and toss the RFP. IBM might try a bid, but usually the "Unix" bit would cause them trouble. [This was well before any serious IBM effort in Unix].
Then they'd print a bunch of copies of these several hundred page documents up and mail them to IBM, Honeywell, Wang, DG and DEC and so forth for bids.
The guy at (say) DG would get this, see that the Govt wanted a Vax, and toss the RFP. IBM might try a bid, but usually the "Unix" bit would cause them trouble. [This was well before any serious IBM effort in Unix].