I have a similar lid on a preserve dish and that is chrome; it too has a pieced base. Your lid looks far too shiny to be vintage aluminium, which corrodes and dulls very slightly. I suggest it fits too well to be a marriage. Metal fittings were all the fashion at one time so there is no reason why a wholesaler shouldn't have bought the barrels without the glass lids - Sowerby would have sold them whatever they wanted...
Undoubtedly, the little lucite knobs were sourced from somewhere else