The Angelus Organ: Tuning organ to 440Hz : The Plan

Introduction

A couple of years ago I bought an old reed organ which was still in pretty good state for its age. The organ is manufactured in the United Kingdom at the end of the 19th century.
The reason I bought it was to use it in our Neil Young Tribute band.
After a mechanical restoration, I introduced it to the band.

There was one problem. It was not tuned with 440Hz as reference. At the end of the 19th century there was no standard for tuning instruments.
As a result it could not be used with other instruments. Guitars can be tuned differently. So that could have been a workaround.
But Neil Young uses his organ together with his harmonicas. And harmonicas cannot be tuned.

So the organ ended up in a corner collecting dust.

The plan is to tune it to 440 Hz reference tuning, so it can be used together with other instruments.