What exactly is patina?

Were old handcuffs brown when they were made? People say some cleaners fetch off the patina. So what is it? A protective coating that was added or something?

No expert but it happens when the plating comes off and the metal oxideses and grows a suface rust over the cuffs. No they would not be brown from new

Were old handcuffs brown when they were made? People say some cleaners fetch off the patina. So what is it? A protective coating that was added or something?

Do not remove it or polish anything, as the value sometimes is cut by half by doing so.

Howy
Cincy

Were old handcuffs brown when they were made? People say some cleaners fetch off the patina. So what is it? A protective coating that was added or something?

Patina --> a green or brown film of oxide formed on the surface of a metal, usually due to a combination of aging and usage. Patina on vintage restraints usually enhances value, so do NOT try to remove it. The problem comes in when cheap "knock-offs" are chemically aged, then passed off to neophyte collectors who pay premium $$$$, only to find their purchase is virtually worthless ......

Were old handcuffs brown when they were made? People say some cleaners fetch off the patina. So what is it? A protective coating that was added or something?

If they can make chemical time, they need to make chemical anti-time and market it to older women. That aside. My preference is modern handcuffs and to collect them for myself, not for what they may be worth down the line. So if I had some older ones, I would want them looking as new, as close to the look that was intended by the manufacturer as possible. So I would say, if you are collecting them for valuable reasons, keep it as is but if you like me collect things for your own enjoyment and you like new shiny things, I would clean them up and polish them with that wax polish the british museum made to keep them as fresh looking forever. All about what you want to do, what your priorities are and purposes for the purchases are.

Were old handcuffs brown when they were made? People say some cleaners fetch off the patina. So what is it? A protective coating that was added or something?

If you were to buy an historic item and remove its age, its history, its value; then you are doing a dis service to collectors of those items. Remember you are only a custodian of the item for your short life.

Were old handcuffs brown when they were made? People say some cleaners fetch off the patina. So what is it? A protective coating that was added or something?

Patina
From Wikipedia, the free encyclopedia
For the village in Estonia, see Pattina. For the United States Navy ship, see USS Pattina (SP-675).

Copper roof on the Minneapolis City Hall, coated with patina

The Dresden Frauenkirche, with black patina on the older stones.
Patina (/ˈpætᵻnə/ or /pəˈtiːnə/) is a thin layer that variously forms on the surface of stone; on copper, bronze and similar metals (tarnish produced by oxidation or other chemical processes);[1] on wooden furniture (sheen produced by age, wear, and polishing); or any such acquired change of a surface through age and exposure. Patinas can provide a protective covering to materials that would otherwise be damaged by corrosion or weathering. They may also be aesthetically appealing.
On metal, patina is a coating of various chemical compounds such as oxides, carbonates, sulfides, or sulfates formed on the surface during exposure to atmospheric elements (oxygen, rain, acid rain, carbon dioxide, sulfur-bearing compounds), a common example of which is rust which forms on iron or steel when exposed to oxygen. Patina also refers to accumulated changes in surface texture and colour that result from normal use of an object such as a coin or a piece of furniture over time.[2]
Archaeologists also use the term "patina" to refer to a corticated layer that develops over time that is due to a range of complex factors on flint tools and ancient stone monuments.[1] This has led stone tool analysts in recent times to generally prefer the term "cortification" as a better term to describe the process than "patination".[3]
In geology and geomorphology, the term "patina" is used to refer to discolored film or thin outer layer produced either on or within the surface of a rock or other material by either the development of a weathering rind within the surface of a rock, the formation of desert varnish on the surface of a rock, or combination of both. It also refers to development as the result of weathering of a case-hardened layer, called "cortex" by geologists, within the surface of either a flint or chert nodule.[4][5]