This is a very, very rare amp from Dynacord. Dynacord was founded in 1945
(the brand name appeared later in 1948). The company started with smaller
amplifiers and cinema amps and became famous for its musical instrument amps
and public address systems. A great history can be found (also in English)
/ stereo amps made by Dynacord are ultra rare and I have only seen the
“Concert” tube amp once in over 20 years.
Obviously the "Concert" was also sold as ST14 as I was told from Sweden.