I've been roasting standing rib roasts and racks of lamb at 175 for
about ten years, and posting with links to pictures in rfc.

I dry age for up to a week. Sear the outsides straight from the
refrigerator. Pop into a 350 oven for 15 minutes, then reduce to 175.
Pull it at five to ten degrees below the target, depending on roast
weight. Allow to sit for at least half an hour.

For a five pound roast (for two of us), pulling at 124, I get a rise
to about 130, and perfect medium rare from edge to edge -- around 1/8
inch of grey edge.

Roasting at 225 is almost as good, but about 3/8 inch of grey egde,
and a bit more variation in the pink.

The key point is knowing your oven. You need an oven that will hold
temperature within five degrees on the low side to go below 200.

-- Larry