Is This A Carrier Mark On Back? Is It Common?

Trying to learn more about postal history.

It seems so,
see last post by Greg
https://goscf.com/t/49601#429113 br /
https://goscf.com/t/64735#562723 br /

No drop fee of 1¢ so thinking it wouldn't be a carrier mark? 3¢ paid the city to city fee.

Am US Newbie, I do not understand that.

ASKPHIL:
CARRIER BACKSTAMP : US Postal Marking of 1870-1890 used in some large Post Offices to backstamp mail handled by carriers

Also noticed the hand stamp even says "carrier", but 99% sure it's a receiving mark since the cover states "Received & answered" on the same date as the back stamp.

Probab;y NOT a receiving mark but applied when letter given to a carrier for delivery.

Found on the internet:

"At the intersection of Blue Hill Avenue, Washington and Warren Streets, Grove Hall links Dorchester and Roxbury. Residents have been attracted to the area because of its proximity to Franklin Park. Grove Hall's residential and commercial growth increased in 1870 after Dorchester was annexed to Boston, and became the heart of one of the city's busiest commercial streets."

The question now becomes did Boston have carrier service in 1867 that served this outlying area?