Hi Jane
Usually the legal and beneficial interests in a property vest in the same person - they are fused.
However, sometimes the proprietary interests are separated.
So: if A holds property on trust for B, the legal interest vests in A; but B (as beneficiary under the trust) has a proprietary interest recognised in equity as a beneficial interest.
Accordingly you could not simply look to documents of legal title (title deeds, land registration etc) in order to ascertain the full picture of the proprietary interests in real property. Sometimes therefore there would be need to look at evidence of beneficial ownership and/or to seek a declaration thereof.
On to your document:
Sometimes a transfer of equity takes place between two or more co-owners.
However, in your case it sounds more as though there was an arm's-length conveyance. In that case the vendor may have been making a declaration of beneficial ownership in order to make clear that the conveyance was of the whole legal and equitable title. In order to transfer legal title, the vendor would have had to hold legal title himself.
It's not quite clear, from what you say, what the document was purporting to transfer.

Also whether the land was registered or unregistered land following changes to the law brought about by the 1925 legislation.