The Nickel chips used in electroplating are attracted to a magnet. I am going to bring a magnet to work this morning because I have wondered the same thing. I have only been doing plating for over 30 years you would think I would know these things, or maybe I do and forgot.
Whatever it is plated with doesn't add any value to the coin, it is considered damaged after it left the mint. There seems to be a lot of plated cents from the 1950's, don't know what that is all about!
Take it out of the flip. Weigh it. Genuine steel cent: 2.70 grams. 950 copper cent: 3.11 grams. Copper plated zinc cent: 2.50 grams. It is missing all the visual indicators of a dime planchette struck by cent dies, so I will discount the possibility.
My guess is a genuine 1956D that has been plated. Depending on the plating metal, and the plating thickness (think in terms of microinches), the weight could be as high as 3.20 grams. Do an internet search on making silver pennies, making gold pennies, and other such terms. You might be surprised what we did in grade school 45 - 50 years ago.
Time for more coffee. I have a 2 for 1 coupon from Dutch Bros.
Well, I used a neodymium magnet either N52 or N54 on a half dollar sized coin that was plated Nickel for 35 minutes and it barely lifted it by the edge. In fact I think it is one of the ones they give to people in AA after being sober for so long. I know of no other metal attracted to a magnet used in electroplating. I think yours must be Nickel and no Silver it is hard to tell the difference unless the Silver tarnishes. Just how strongly did it stick to the magnet?
Never heard of micro inches we plate in millimeters. Most heavy Gold is only between 3 mills and up to 40 which is very rare, maybe a chain that will be worn.
I will claim no knowledge of what type of materials you plate, but I will take issue with some of the terms you use. Thicknesses of one millimeter and one mil are vastly different. One millimeter = 39.37 mils. One inch = 1000 mils.
In both jewelry and electronics, plating thickness is normally expressed in terms of microinches or micro millimeters.
Base metal plating for industrial applications is very different and demands greater thicknesses.
Please remember that the topic is a one cent piece that many here believe to be plated. The cent started life at 1.52 millimeters thick.
Yes you are right about the micro millimeters and the amount I plate on, is for the whole rack not one piece. They can barely speak English and you think they are going to write micro millimeters on the work tag? The pennies must be Nickel plated it can't be anything else. The penny would not triple in size after being plated, my bad.
The pennies must be Nickel plated it can't be anything else. I could do up a couple a thousand in a barrel plater at break time if the are worth anything.