Need help identifying Dutch silver dish/tray

Ok, this is not British silver (but there’s no section for Dutch silver).

I have this dish that bears the insignia from the Rotterdam Lloyd steam ship and on the back are the following marks “S” (or perhaps it is an “8”) “B” GERO 90. The “B” and “90” have circles around them.

View image here: … ay_web.jpg

I was told this is silverplated with 90 grams of silver for 12 similar dishes (or such), but there was no answer on what the “S” or the “B” signify. Another curiosity is why it is so thick and heavy if it is merely silverplated…it is 8.5"long x 5.25"wide x 9/16" tall and weighs .56 lbs (or 9 oz).

Can anyone help me with these questions, confirm that it is silverplate, and does anyone happen to know the value or rarity of this particular type of dish?