Many moons ago....
You used to build up your own EWD's placinga kinetic siren into cqr box ect...
We used to have a bell module w/o a cut off timer which had the electronics in a beige plastic case but the electronics filled over with an expoy resin,
I have a little electronics projects & wanted to cover the cobbled together ebay tat so its weather proof & not recognisable as a lash up