No bandoneon is more loved — or more faked — than the one stamped AA: Alfred Arnold of Carlsfeld, Saxony, the instrument the tango was built on. Around forty-four thousand Arnolds left the factory in all; an estimated thirty thousand of them crossed the Atlantic to Argentina and Uruguay by 1945. And uniquely among bandoneon makers, Arnold’s numbers can be dated — inside one clear window.

The window: 1931–1941

The years of research by collectors and restorers (Carsten Heveling’s published analysis is the standard reference) have established that Arnold’s six-digit serials, 100,140 to 112,625, fall between 1931 and 1941. Even better: many of those instruments carry a date stamp — a small stamp on the mounting base of the keyboard (the Montierboden) that gives the actual day of assembly. If your Arnold has a six-digit number, you are in the datable zone; open the treble side carefully, photograph the base, and read.

Premier instruments carry the same numbers, from the same Carlsfeld benches — Premier was Arnold’s export brand, not a different factory.

The traps

Two kinds of numbers on old bandoneons are actively misleading. The numbers stamped on the outer case were added by South American importers and dealers — often arbitrarily, sometimes to “improve” an instrument’s age, and they should never be used for dating. And the internal B and D numbers (visible on the reed blocks) are part-matching marks, pairing a bass half with its diskant half during assembly — not serials. The only genuinely chronological number is the factory serial on the frame, in the documented blocks.

Outside the window

Arnold numbers below the six-digit block, and the later VEB-era production (the factory continued under state ownership until 1964), do not follow a datable sequence — the archive says so rather than guessing. The sibling firm ELA (Ernst Louis Arnold) is partially datable too: its serials 18,585–37,850 fall in roughly 1926–1939. Beyond that, bandoneon dating returns to the feature method — construction details, reed-block stamps, and the instrument’s furniture.

Before you buy one

Two minutes with a serial number is the difference between a 1930s Carlsfeld instrument and an undatable postwar box wearing a hopeful stamp. Run the number through the Alfred Arnold lookup first; the page also walks through where the number lives and what to photograph.