Greg,this certainly looks like the old Merit mouldings right down to the way that the sprue is laid out,I doubt whether anyone would bother to re-tool a new Walrus.
I remember a weekly television series that featured the following Avro 504,Tiger Moth,Walrus,it showed some old boy smoking a pipe in a shed painting each of these models with a gallon tin of paint in front of him ! whilst he appeared to apply layer after layer of paint he related a true story about each aircraft,each kit was a Merit one,they were practically the only 1=48th scale kits around back then,real masterpieces for their time,you have a piece of modelling history before you there.
Vickers Supermarine Walrus. 
VH-ALB Vickers Supermarine Walrus. The Supermarine Walrus started life as the Seagull,a folding wing biplane with retractable landing gear and powered with a Napier Lion engine.The experimental installation of a Bristol Jupiter IX radial engine led to the Seagull V powered with a Bristol Pegausus IIM2 radial engine,of which 24 were ordered by the Australian government,through this the aircraft was adopted by the Fleet Air Arm under the name Walrus Mk.1 and these were built by Supermarine with metal hulls of which production totalled 746,of which 461 were built by Saunders-Roe,this number including 191 Walrus II aircraft with Saro wooden hulls and the Bristol Pegasus VI engine,entering service with the FAA in 1936 the Walrus was stressed for catapult launching and as such equipped battleships of the Australian,British & New Zealand navies,the aircraft operated in almost every theatre of WW2 playing a significent role in air/sea rescue with the R.A.F. Finally post war the aircraft was used by the Argentine air force of which eight aircraft were supplied. Max speed: 135 mph. Service ceiling 17,100 feet. Range 600 miles. Weight empty:4,900 lbs. Max take off weight: 7,200 lbs. Wingspan: 45 feet 10 inches. Length: 37 feet 10 inches. Wing area: 610.0 square feet.