That would probably be the first change of manufacturer of Bartali bikes. The website of the Citta di Novi Ligure,
http://www.comune.noviligure.al.it/servizi/Menu/dinamica.aspx?idArea 59&idCat89&IDe02
has a photo of the Bartali team saying they used Santamaria bicycles - an association that started in 1949 when Bartali left Legnano. It says that the relationship continued until 1954 when Bartali retired from racing, so it may be that the bike in the museum is actually later than the stated 1953. I have seen another reference to Bartali-branded bikes being made by Santamaria but haven't managed to track it down yet.
Hugh Thornton Cheshire, England
--- On Tue, 18/8/09, Angel Garcia wrote:
From: Angel Garcia <veronaman@gmail.com>
Subject: [CR] What can anyone tell me about Bartali (bike)?
To: "CLASSIC RENDEZVOUS" <classicrendezvous@bikelist.org>
Date: Tuesday, 18 August, 2009, 8:21 PM
The CicloMuseo Gino Bartali has what it says is a 1953 Bartali "made by
the Fratelli Margherita of Celle Ligure".