If a Last Will and Testament mentions a memorandum, the memorandum most likely should have been attached to the finalized, processed document.
Whether or not that Will is legal and valid depends on upon the situation and the document.
If the document that was filed or processed possesses all of the requirements to create a valid will — i.e. signature, witnesses, notary clause — that goes towards validity.
The next question is then whether or not the Will, read without the memorandum, encompasses all of the bequests that the Maker intended.
A qualified attorney should be consulted if there are specific questions about what was or could have been contained in this memorandum, or whether or not the local probate court has rules addressing the absence of the memorandum. See Standard Legal’s Attorney Find page to find a local attorney for FREE.