The trade name of D.Walter & Co. who produced a range of stage lighting equipment which was popular in schools. The company was also known as Walters Lighting and J.D. Walter.
They were included in a stage lighting package by the Gaumont British & Kalee company that had the contract to supply equipment to schools in the East Suffolk area (and other areas).
As well as manufacturing under the name DeWalco, they also produced fittings as 'Brite-Lite', making decorative light fittings and architectural cove troughing & exterior illumination.
They were based at 107 Newington Causeway in London before moving to 61-63 Lant Street, London SE1.
By the mid 1960s, they were seen as part of the Gaumont British-Kalee group (to be confirmed) which was bought out by Rank Audio Visual - see that page for more DeWalco catalogues.
Thanks to Jim Laws, Tim Hatcher for information.