Mainspring for Angelus 240 Sonnerie (Striking Train) – Swiss NOS

New old stock mainspring for the striking mechanism (Sonnerie) of the Angelus 240 alarm movement, 1.80 x 0.09 x 300 mm. Not for the going train.

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Angelus 240 Sonnerie Mainspring

New mainspring (NOS) for the rare Angelus Caliber 240 Sonnerie (alarm). High-quality Swiss part for the restoration of your 8-day vintage timepiece.

🚨 IMPORTANT NOTICE BEFORE PURCHASING:
Please note that this is exclusively the mainspring for the striking mechanism / alarm (Sonnerie).
This spring is NOT suitable for the going train (Mouvement / timekeeping)! (“Not for Mouv.”)

Why is this exact distinction important?
The Angelus 240 (8-day movement) in its alarm version features two separate barrels with completely different requirements:

• The going train (Mouvement): Requires a very long spring for an even, slow power delivery over 8 days.
• The alarm (Sonnerie): Requires the spring offered here. It is specifically designed for short, high-power bursts to allow the mechanical hammer to strike forcefully.

Incorrectly installing this Sonnerie spring into the barrel of the going train will lead to extreme rate deviations (knocking/overbanking) and can severely damage the delicate pivots in the wheel train of your caliber. Please ensure before purchasing that you explicitly need this replacement part for the alarm function.

Compatibility & reference photos:

• Fits: Both alarm versions of the Angelus 240 caliber (key-winding and crown-winding, approx. 1936 – 1970). The dimensions of the alarm spring are identical for both variants.
• Reference photo: To avoid any confusion, I have added a reference photo of the correct alarm movement to the main image gallery. You can clearly see the two separate barrels required for this part. Please compare this with your movement.
• Height: 1.80 mm
• Thickness: 0.09 mm
• Length: 300 mm
• Ø spring: 8.50 mm
• Condition: New (NOS)
• Origin: Swiss Made