Advice on tubular tyres

the tread was hand glued (colle main) onto the body on the tyre... this seems to be the hall mark of excellent tyres (Veloflex use this method today)

Likely because this is the method until then employed by Vittoria, who sold their equipment &c to Veloflex when they moved production out to Thailand where, of course, handwork is available at lower labour rates than in France