The Dolnet Series I
If it is true that the first Dolnet saxophones were produced in 1888, these are definitely not the first saxophones that Dolnet produced, but are the earliest I've been able to find. It is possible that, like Buffet, their serial number chart has changed a couple of times.
Based on these horns' keywork, I would estimate they were made in the mid- to late-1930s.