The interest in vintage saxophones has been important for a while, and the interest rose intensely over since 70s.
This mainly because many companies were cost cutting
and moving factories--Conn to Mexico in the 60s,
King cheapening in the 60s too, Buescher getting bought our by Selmer .
In addition when Selmer Paris did not manage to follow up with a good enough successor to the Mark VI,
the interest in both the old Mark VI and other older vintage saxophones increased further.

Vintage saxophones have normally a larger bore so the sound is broader, a little darker and warmer.
A new modern saxophone has smaller bore and therefore a little brighter sound also described as a thinner sound.

The table below shows the most commonly used materials and their characteristics.

Material Alloy Description 
Brass copper and zinc The majority of the saxophones are made of brass. Typically, student brass horns will be made from the lesser copper mixed brass, known as “yellow” brass, whilst higher quality brass with a higher copper content will be referred to as “gold” brass
"Yellow" brass 50-70% copper Tighter, brighter timbre. Yellow brass is also cheaper to manufacture so is most common place in student horns
"Gold" brass 70-80% copper. The extra copper content lets the material resonate more freely, allowing for a broad, rich tone.
“Gold” brass is what most professional horns are made from
"Red" brass 85% Copper Red Brass givines a rich colour pallet together with added warmth and projection.. However there will be less flexibility in this tone
Bronze Copper and tin.
Typically 88% copper and 12% tin
Bronze is our most popular non-brass metal choice for a saxophone. This produces a denser material with significantly higher resonance than Brass. This resonance will give you a horn full of warmth, colour and complexity

Nickel Silver
18% nickel, 62% copper, 20% zinc Nickel Silver is incredibly dense, and has huge resonance, but not in the same way that Bronze or Solid Silver will respond. What the heavier inclusion of Nickel will give you is brightness. In spades. These horns absolutely pop and give a big response aurally.
Tonally, this boldness gives the horn an aggressive edge, perfect for a soloist or someone interested in those big rock and roll/funky noise! Resistance wise, the horns are pretty free-blowing, especially for a material so heavy. They will be noticeably heavier then brass models, and certainly louder.
Solid Silver   Solid Silver is extremely dense and soft, so has the highest point of resonance on this list. What this gives you is a thick, full sound that has tons of warmth across the whole spectrum. This warmth is most present at the bottom end. The tone produced isn’t as piercing, making solid silver fantastic for ensemble work, especially in a Classical capacity where Saxophone tones can come across as a bit harsh, but Solid Silver will need a little more pushing for more electric work. 
Copper   Though the Copper horns I have played are full of poke and aggression, there is a sense of depth to the tone that feels very similar in response to Bronze instruments. Copper is certainly a material to consider if you are a player looking for something truly different.