An entry in the BNA Gloucester Journal - Saturday 21 June 1862 indicates that this may have been a turnpike gate near Symonds Yat.

DEAN FOREST TURNPIKE ROADS.

NOTICE is hereby given, that an ADJOURNED and SPECIAL MEETING of the TRUSTEES of these Roads will be held the Angel Hotel, in the Town of Coleford, on Wednesday, the 9th day of July next, twelve o’clock at noon, for the purpose of considering the propriety, and if thought expedient, of ordering and directing the removal and discontinuance of the present Turnpike Gate, near Symond’s Yacht, called “ Redding Horn,” situate within the said Trust ; and of considering the propriety, and if thought expedient, ordering and directing the erection of the following Turnpike Gates or Chains, with all necessary Toll-houses, Outhouses, and other conveniences, thereto respectively, namely, one on the Road leading from Coleford to Symond’s Yacht, at a point some 140 yards nearer to Coleford than the at present existing Turnpike Gate at Redding Horn aforesaid, and one on the Turnpike Road leading from Park End to Blakeney, near the present Turnpike Gate on Moseley Green, both which said proposed Turnpike Gates or Chains will, if erected, be situate within the above Trust; and that the same Tolls may be taken at the said Gates or Chains respectively as at other Turnpike Gates or Chains within the said Trust.

JAMES WINTLE, 19th June, 1862, Clerk to the Trustees.

This site contains information about turnpike gates and mentions one called Reddinhorn in the civil parish of Coleford. I don’t seem to be able to get the OS co-ordinates to match though.

http://www.turnpikes.org.uk/Tollhouses%20of%20Gloucestershire.htm

And on Streetmap is a place called Redinhorne just south of Symonds Yat Rock.

This map, c1880, marks Redinhorne as a whole stretch of road south of the Rock,

http://maps.nls.uk/view/101453325