Copper is generally considered to be a soft metal, meaning it can be worked without heating. Over a period of working the metal in this way it can ‘work harden’. This means that the molecules within the copper are compressed and irregular in their arrangement. This causes stress in the metal and eventually cracking the metal along these stress points. In order for the copper to be worked to any extensive degree it must be annealed. This process involves heating the metal and then rapidly cooling it in water. The cooling stage is known as quenching. By heating the copper, the molecules in the metal are relaxed, and able to align themselves in a more uniform fashion. This allows for easier shaping of the metal. In order to keep this uniformity within the metal, it is cooled instantly. This prevents the molecules from moving around and causing tension in the structure of the metal. While iron and its alloys also work harden, the annealing of those alloys is opposite that of copper-slow cooling softens steel and iron.

What does this all mean to say? It appears yours are “Plating Aluminum with copper” and the marking also appears to be
5 – then grade of – P – then the reconfirm # 5 in roman numeral > V = 5PV.

From [phone number removed] Denmark did expand these type of clinical coasters made in (now Czech Rep), Hungary and India. Clinical labs used plain coasters (similar to yours) to hold round glass specimen cases that would hold into such coasters too.

Best of luck in your continued research.

Those definitely are used in laboratory clinics to hold specimens. The glass sandwich cases fit right into these copper metal coasters to avoid spread of germs or contamination from contact. The 5pv were made for Denmark distributed in India. I would not list to sell as coasters for regular use but would consider listing as vintage medical collectibles.

My goodness, Montrose! If they are actually specimen dish holders, no wonder I could not find them. The only good site I found online today was Oldcopper.org, by Vin Callcut. He had an extensive list of metal maker’s marks, but not this one.
If they are plated aluminum, then they still would not attract a magnet. Plated aluminum is something I never would have thought of!

Thank you also, Angelica. Searching for “SPV Copper from Denmark” I immediately found a trinket on eb— with the exact same mark. The seller claims it has been in the family for generations, made in [phone number removed].

Well…still a mystery, but getting closer!
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last [URL removed] Thanks, Process. Guess I will hang on to them for another 40 years. LOL… At least they don’t take up much space. I do have some other antique laboratory items…somewhere.