Pens that appear to be Wirt pens are found with the brand “PHENIX”. No patent dates or city are imprinted on the pens. They have unvented feeds. The shape of the feed is very “Wirt-like” but is unvented.
I have two Wirt PHENIX pens that resemble post 1903 underfeed Wirt pens.
I have found online pictures of a both a black hard rubber and a mottled hard rubber PHENIX pen that is clearly a Wirt hump filler. Apologies to the photographer for usage here.