That's how the key verification in Half-Life GOTY works.

def keyVerify(key="YouLikeBoysDon'tYou?80085-2137-2137") -> bool: # example key
	assert(len(key) <= 0x40)
	key = [x for x in key if '0' <= x <= '9']
	assert(len(key) == 0xd)

	acc = 3
	for i in range(0xc):
	    acc += int(key[i]) ^ (acc << 1)
	is_valid = (acc % 10) == int(key[0xc])
	return is_valid

So as you can see the code only cares about numbers, it skips other character.
The key is valid if (acc % 10) == int(key[0xc]), so we have like 1 in 10 chance to just guess the key.
Btw some reddit user states that "The cd keys used to be stamped on the outside of the box" which is kinda funny.