thanks for resurrecting this old thread. just some thought on it. we have settled on my 53 being a Armbruster. the key factors were the 5 stripes on the glass and the tunnel lights. I have only seen 2 other ambulances with the same tunnel lights as my 53. both were unlabled as to builder. one the 57 GMC panel and the other a short 54 chevy sedan delivery. I could match up the 54 with a flyer from Armbuster in 54. I do not know where the 57 is right now but the 54 is in Lenny Langlois collection. finding 3 rigs with the same features shows a number were make like that. being able to match one of them up with a advertising from the company cinches the deal. Armbruster has them labeled as a utility ambulance