The chassis can become very rusty on some old Silvias, this new chassis will bring your espresso machine back to its former glory. I would also advise replacing your jet breaker at the same time as I believe the failure of this part is the cause of the rusty chassis, part number 10090002.
You will also need to buy these rubber feet to go with your new chassis https://www.homecoffeemachines.ie/products/rancilio-silvia-support-foot-set-36310008
And while you are at it you should replace the seals and gaskets on your machine, she will be like new, here is the kit with everything. https://www.homecoffeemachines.ie/products/rancilio-silvia-refubishment-kit