Please don't use chrome on parts for an automatic musical instrument
made before the 1950s, for two reasons.  First, it makes the parts
thicker, so you'll spend a lot more time removing it from shafts,
holes and old threads before you'll be able to reassemble the parts.
Second, it doesn't look original.

When a manufacturer wanted a cast iron or machined steel part to
look smooth and shiny, it sometimes applied copper to the part, buffed
the copper to a high polish, and then applied nickel plating.  This
produced a beautiful smooth finish, and was used on rounded things like
piano pedals, the pressure bar that presses the upper ends of the
strings to the piano plate, the heads of the plate bolts, certain coin
slots and control knobs, etc.  Relatively few platers apply copper
today, because they don't want to deal with EPA restrictions on
handling the cyanide that is needed for this process.

Mechanical parts inside the piano were almost never highly polished.
There, the parts usually had a very thin coat (or "flash coat") of
nickel -- sometimes shiny conventional electroplating, and sometimes
a duller, grayer "Watts nickel".

Today, "Watts nickel" means different things to different platers.
My local plater's Watts nickel is black, and can't be polished to
a uniform color on a rough cast iron piece.  I've seen other batches
of Watts nickel that looks similar to the color of aluminum ("silver")
spray paint.  In fact, one Wurlitzer roll changer that we restored
with Watts nickel in the early 1980s has elicited this comment from
several people: "Why did you use paint instead of replating it?"

Other Watts nickel has a beautiful, soft patina identical to the
looks of an original Philipps roll changer.  Investigate what you'll
be getting before requesting "Watts nickel" on a large batch of parts!

To me and many of my customers, one of the worst looking things that
can be done to a player action is to buff the sharp edges off the
mechanical parts and then apply a thick coating of electroplated
nickel.  I call parts that have been subjected to inappropriate heavy
buffing "puffy parts," and to me they're ruined, just as a rare coin
is ruined by buffing its detail away!

Want to diminish the value of your piano fast?  Send the stamped and
cast metal parts to bumper shop with large muscular men running giant
buffing wheels!  The worst of the worst is to do this to coil springs,
flat steel springs that originally were blued, cast iron Seeburg parts
that originally were painted silver, Cremona parts that were originally
painted gloss black, etc.

For mechanical parts that were nickel plated but not highly polished,
I recommend "electroless nickel plating" from a shop that specializes
in this.  It can be applied in a very thin layer that doesn't require
retapping all the holes.  This is especially important when restoring
parts for certain German orchestrions, in which much of the hardware
has obsolete metric threads for which taps and dies are no longer made.

Certain platers dislike electroless nickel because it doesn't fill
imperfections in the metal and doesn't produce a smooth shiny surface,
but the original unpolished finish is exactly what we're trying to
duplicate for many mechanisms.

Regarding cosmetics, nickel plating has a faint yellowish tint, while
chrome has a bluish color.  It is true that parts are nickel plated
first, before the chrome is applied, but the color difference is
obvious if you hold samples next to each other.  The idea that chrome
is transparent might be a misunderstanding of the fact that the
smoothness of each coat (but not its color) will telegraph through to
the next coat, so if the underlying part isn't smooth, the nickel won't
be smooth; if the nickel isn't smooth, the chrome won't be smooth.

If a shop inadvertently puts chrome on your parts, the chrome can be
stripped off leaving the nickel intact, at least if the shop has the
right chemicals.

Even when a mechanism has conventional threads, for which taps and dies
are available, reassembly of an intricate, complex mechanism is much
easier when the parts don't have a thick coating of electroplated nickel
built up at the higher voltage points, including ends of shafts.  Some
of the most difficult and expensive re-restorations that we've done
have been Wurlitzer automatic music roll changers that had been
stripped poorly, buffed, and plated in thick copper, nickel and then
chrome in a previous restoration.  By the time the old materials and
intermediate layers of rust and green corrosion were stripped away,
the original threads were damaged so badly that a great deal of extra
machining had to be done before the new plating was applied.

For more information, please go to the Musical Box Society web site
at http://www.mbsi.org/  to see Part One of my recent illustrated
article on Wurlitzer roll changers, reprinted from the journal,
"Mechanical Music", of Jan/Feb 2006.  (On the opening page, click on
"Publications."  On that page, scroll down to the heading "Mechanical
Music Articles" and you'll see the title of the article.)

As I said at the end of Part Two in the Mar/April issue, "A Wurlitzer
roll changer isn't a car bumper or 1950s jukebox.  Its castings and
machined parts were never polished to look like high-gloss piano
pedals, and plated with chrome.  If you must replate a roll changer,
please see to it that your plater understands how it looked when it
was new, and how to duplicate that look, using thin nickel plating
only.  Please save the buffing, rounding, high polish and chrome for
your 1953 Buick or Seeburg M100A."

Art Reblitz