Original Winchester bullet molds are caliber specific.  Example:  A Winchester mold marked .45-60 will not work well in a .45-75 because the bullet weight isn’t the same.  The .45-60 is loaded with a 300 gr. bullet and the .45-75 with a 350 grain bullet.  Winchester had a great way of marketing bullet molds.   There were several .45 caliber Winchester cartridges that used a 300 grain lead bullet.  As an example, the .45-60, .45-70 and .45-90 were all loaded using the same bullet.  You could have used the same mold to cast bullets for all of these different calibers.  But if you did that, Winchester wouldn’t sell nearly as many bullet molds.  For that reason, they marked every mold with a specific caliber designation.  I’ve used original Winchester molds and tools in a dozen or more calibers, to reload for some of my guns.  Out of curiosity, I’ve weighed many of these bullets to see how close they come to the weight Winchester listed them at.  I’ve found most of the molds to be very consistent for weight.   In other words, a 2nd model, 3rd model, 4th model and 5th model Winchester 350 grain bullet mold in .45-75 caliber, will all throw a bullet in 349 to 352 grains.   New bullet molds for these old calibers, can be had from RCBS, Lyman and several other companies.  Bullet shape and specs are nearly identical to original Winchester factory loaded ammo.

Win4575 nailed it.

Here is a photo of a Lyman mold block #457192 that casts a 350 grain flat point bullet. Before it was purchased by Lyman, this mold would have been made by Ideal.  Also in the photo is an original Winchester 4th model mold labeled .45-75 that cast the bullet shown.  These two molds are virtually identical. 

I don’t believe the .457192 is still in Lyman’s catalog.  From what I have read it was in their catalog into the 1970s!  I found this one at the Denver CGCA show a number of years ago.