IRT Brooklyn Line Near the Portal

Hi Folks:  In subchat, there was a conversation about the middle track at the portal east of Utica Avenue.   I found by accident this trackmap published by the New York Division Bulletin from their July , 1991 edition  (Vol . 34 Number 7).  This is from an article titled "IRT Brooklyn Line" by Bernard Linder.    The map appears on page 4 and is shown above in the top right corner.  Notice the the middle track connects with both the upper and lower levels east of Utica Avenue and the stub tracks extends somewhat east of the portal.