RobertMG
The US 206-209 concurrency is controversial.  See https://www.usends.com/milford.html .  Signage may be expected to vary.  Officially US 206 was never designated from its current junction with US 209 at the bridge exit to Harford St.  Until 1946 US 206 was concurrent with US 209 from Broad St. east along Harford St. to Front St. and what is now Milford Beach Rd. to Metz Rd.  Later a new Montague-Milford Br. was built and connected, cutting off US 206 south of Metz Rd. and rerouting US 209 off Metz Rd., Milford Beach Rd., Front St., and a portion of Harford St.  Signage in this portion is by the National Park Service.