Years ago I cast 125lb of soft lead ingots that looked just like yours.Pretty gold color,they came from a shower pan that someone gave me.At the time I had lots of ww & telphone cable lead.I dumped the pan out in the pasture,to deal with later. 20 years later I got around to it.In this east Texas suger sand it was covered up grass growing over it.It took a rip plow and a little time to find it.When melted and cast it was gold.My ingots were not fluxed good enought.I was in a hurry,the pot was not hot enought.They had alot of sand still mixed in 6 mo. later I remelted and did it right,It went from gold to just plane lead,wish I had saved one ingot to display.
Yours may be like mine cast with a poor fluxing job.