Patina?

A few years ago I was going to strip this all back, hammer out the dings and repaint it.  A job I wasn't looking forward to.  A Blipper even said he could provide colour references as he worked at the original factory that made it many decades ago.  Then a Wren started to nest in it (front left corner access) so I didn't bother.  The next time I thought about it I saw an antique programme that said 'patina' was all important so it escaped another refurb.  Now I'm running out of excuses!

For the curious...  It's an air vent from an old boiler house and it covers a septic tank hatch in the garden.