Interesting! This is what IGC have on him:

Name Joseph Forrestall Smythe
Other Names J F Smythe Ltd
Address1 13 Blackwellgate
Address2 12 Horsemarket
City/Town Darlington
County Co. Durham
Country United Kingdom
Trade Gunmaker
Other Address Stockton-on-Tees; Middlesbrough.
Dates 1885-1930

Notes

Joseph Forrestall Smythe may have been apprenticed to William Greener from about 1850 to 1860 before he moved to Edinburgh to work for Alexander Henry.
In about 1875 he moved to Dublin to become manager of Trulock Brothers (Trulock & Harris) of 9 Dawson Street.

In 1885 he moved back to England and bought the business of Francis Brebner at 13 Blackwellgate, Darlington.

The firm were known for their cartridges, but in 1894 the workshop and shop at 13 Blackwellgate were destroyed in an explosion and Smythe moved to 12 Horsemarket.

In 1899 he opened a branch in Stockton-on-Tees at 21 Dovecot Street, and then another in Middlesbrough at 16 Albert Road. It is believed that the Middlesbrough and Stockton-onTees branches had closed by about 1905.

In about 1913 the firm became a limited company.

J F Smythe died in 1930 and the business was sold to Joseph Pease Ltd who traded until about 1934.

Other Info
The firm sold cartridges under the name of "Smythe's Champion", "Special Champion" (post 1927), "Smythe's Special Load", "The Field" (post 1920), "Durham Ranger" and "Gastight".

Tim