I think that Lyman has actually made three machines, the 45, the 450 and the 4500.
A true model 45 is a very old machine. When it was discontinued I don't know but my uneducated guess would be sometime in the 50's. I looks and works very differently from the 450 and 4500. I have one and like it but, well, they are old.
The 450 comes in two flavors which you can not tell apart. At some point Lyman started making their dies and lubricator's to much closer tollerances than they use to. Thus an old 450 will handle and Lyman or RCBS sizing die. A newer one may not because a newer 450 has closer tolerances and the older Lyman and RCBS sizing dies don't. Unfortunately you can not spot this easily (actually I don't know how you spot this at all).
Newer 450's or the current 4500 work quite nicely. Actually I'm a real fan of both. Simple, easily repaired, etc. The 4500 has a built in heater which you can buy or not as you see fit. It is easily removed. I like that.
The RCBS machine is a Lyman copy. I don't know how touchy it is about tolerances on the sizing dies. Unlike any other lubricator/sizer on the market, however, a new RCBS is guaranteed for life. Break a part on any other machine and you'll probably have to buy the replacement. Break a part on an RCBS and they'll give you the parts you need. I'm sure about this because I've done it.
One other difference between the RCBS and Lyman is the maximum size sizing die that you can easily remove. I don't remember the largest sizing dies that these companies make but other firms make dies for these too up to 0.577. I've got that one.
The problem with the larger size sizing dies is that they CAN NOT be easily removed from the machine. There is a hole in the bottom of the casting through which a rod comes up that pushes a sizes bullet out of the die. It also pushes a sizing die out when you are done with it. The problem is that this rod is smaller in diameter that the hole in some of the larger sizing dies so once you get the die in getting it out can be a REAL thrill. I'm sure about that because I've done this.
The maximum size sizing dies that can easily be removed from a Lyman is about 0.45 I think. Not absolutely sure. The maximum size sizing dies that you can easily get out of an RCBS unit is just slightly over 0.5 I think.
In fairness to these companies they never intended people to be using these sizers on 0.577 diameter projectiles but today with 50-70 and 500 S&W magnums this can get to be a problem.
Personally I'd recommend just about any Lubricator/Sizer on the market except SAECO or Lee. In Lee's case I've just never used one so I don't know how well they work. I'm about to find out, however, because mine came yesterday. In SAECO's case I've used one a lot. Poor leverage and a main gasket that REALLY has problems.
Hope this helps.
