The sapphire glass used on some devices was reportedly made in an apple owned factory, according to Apple terms, using equipment Apple paid for. The actual production was handled by a third party using that space that went bankrupt, but I'd say it counts.

This would be the most significant component they've manufactured in-house though.

That doesn't count because the other company had designed the process, but didn't have capacity to produce at Apple-level volumes. Apple paid for the expansion,and then ditched the company's product (which led to the bankruptcy)