The early models retained the drilled and tapped top while a later produce version had an L-shaped bracket with a picatinny rail which mounted with 2 screws to a breech support bar on the right side. Known caliber combinations .17HMR/20, .22lr/20, .22 Hornet/20 or 12ga, .223/20 or 12ga, & .30-30Win/20 or 12ga Hopefully this doesn't confuse all of you further, but this is really the simplest way to deal with this information.
Models include 24S, 24S-A, 24S-B(not sure at this point it exists but follows logically in sequence so I include it) 24S-C, 24S-D & 24S-E.
Savage 24C: All came only in 22lr/20ga and 20 inch separated barrels; 24C Series M, 24C Series N & 24C Series P all had English straight stocks and toothpick style forearms and had top of tang barrel release lever; 24C Series R had the American pistol grip style stock and top of tang barrel release lever; 24C Series S also had the American pistol grip style stock but the front of the trigger gaurd sliding block barrel release.
It had a single trigger with the barrel selector as a small push button built into the uppor portion of the trigger sliding left to right or visa versa. Known models 24 Series N, 24 Series P, 24 Series S.
Series N and P have top of tang barrel release lever while Series S the front of the trigger gaurd sliding block barrel release.
24V & 24V-A had an unsightly monoblock breech which changed slightly on the 24V Series B and recontoured to a more smooth and eye appealing in the 24V Series C and 24V Series D.
All models other than the 24V Series D were only chambered in .222Rem or .30-30Win.
Savage 24D: (This is one series I'm still figuring out) Separated barrels; Monte Carlo type stocks on some but always with checkering on stock and forearm unlike the standard stocks.
Known models include (24D Series M, 24D Series N, 24D Series P) Savage 24V: All came in only center fire cartridges over 20 gauge; Monte Carlo style stocks (some checkered other not); top of tang barrel release lever; separated barrels; Pay close attention to markings as this is exactly how they appear on the guns themselves 24V, 24V-A, 24V Series B, 24V Series C, 24V Series D.
Savage 389: Made by an Italian Company for Savage, like the 2400 it was shotgun over rifle in configuration.
It came with 2 triggers (one for each barrel so no selector) and was chambered in .222Rem/12ga and .308Win/12ga. 24 Specials (The S in this case refers to "Special"): All came in 20 inch separated barrels; satin nickel finish to receiver, barrels, sights, etc.; all came with rubbed oil finished higher grade wood stocks and a somewhat matching wood pistol grip attachment to replace the stock.
I have also been told by previous employees of Savage that they think some custom chamberings were made on a very limited basis by order (e.g.