Chainsaws

Chris,  I don't know all of the lettering codes but here is some Information that may help from my own experience. A really good source of Information on Bars and chains, as well as sharpening and a selector guide to match up your saw to, and they have tutorials is "OregonChain.com".

RSN = type of Nose on bar (Replaceable Sprocket Nose), there are many types of bar noses, including solid with no sprocket.

3/8 or .375 = Pitch of chain, Note: This is the distance from one link to the next on a chain divided by two, or if you measure from rivet to rivet and divide by two .

.050 = Gauge,  it is the thickness of the bar groove or the thickness of the drive link on a chain that fits in the groove.

72DL= 72 Drive Links, the drive links fit in the bar groove, there are varying numbers of drive links depending on the bar length, width, and bar type.

There are also Mounting codes which will tell you the spacing of the bar bolts, and dimensions of the bar mounting, I suspect some of these other letters and numbers will give you that information. So I hope this helps, and would really recommend reading the tutorials, and information on Bars and Chains at "OregonChain.com" site. There are many manufacturers of bars and chains, and it probably would be difficult to know all of the specific Information from different companies, however many companies that sell Bars and chains will give you Website access to cross reference guides, If you want to buy a similar bar from a different manufacturer.

Also, about your comment on Ebay, there are many individuals who sell parts and pieces, and they are Not all businesses, some are just individuals, and in my opinion may know alot less than you do, so you need to be careful that you know what your buying. Please check out Oregonchain.com, and Hope this helps.