MCO-13 to MCO-15

I have been using MCO -13 for many years and reference the variation column numbers for a lot of my variarations documents.  For example, Ruy Lopez Exchange Variation, MCO-13 col. #40 is:

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Bxc6 dxc6 5. 0-0 bd6...

Do the same variations use the same col # in MCO-14 and MCO-15, or are they all different?

Thanks!

They are all different in MCO-14. The Ruy Lopez chapter is split in three: systems without 3...a6 (columns 1-30), systems with 3...a6 (columns 1-60), main line 5...Be7 (columns 1-42). 5...Bd6 is column 5 in the systems with 3...a6. In MCO-15, for the Ruy Lopez at least, the columns are numbered the same as MCO-14.

Thanks for the info, that's what I needed to know!

My interests also pertain to variations of the Sicilian, French, Nimzo-Indian,  etc, about 20 particular openings in all. 

Is there any other convention being used for opening variation identification 'nowdays'?

Most software uses the Encyclopedia of Chess Openings (ECO) codes. Ruy Lopez codes are from C60 to C99. The Exchange Variation is C68. The first edition of MCO of course predated ECO by many decades. MCO was originally arranged alphabetically. In MCO-2 the Sicilian Defence occupied only six pages! Eventually MCO was arranged by Open (1.e4 e5), Semi-Open (1.e4 other), Closed (1.d4 d5), Semi-Closed (1.d4 other), and Irregular, but still alphabetical (!) within those groups. It's not terrible, but the ECO codes are based only on moves so in most respects the arrangement is more logical. And again, software "knows" the ECO codes.

https://www.chessgames.com/chessecohelp.html

Thanks again!

I've looked at the ECO codes on the link you provided, and at another site - I was surprised that there are a lot fewer ECO coded variants than MCO columns, I tried a couple of my standard variations, and while my Ruy Lopez mapped perfectly to ECO C68 (as you said), my Silcilian Dragon Classical variation (MCO-13 Col #80) did not map to either C73 or C74 for my last 2 moves (7. 0-0 0-0, 8.Be3 Nc6).

Sadly, I've never owned or even seen an ECO book set, I think it was 5-volumes and a lot more money...

ECO has no use now except as a reference for what opening moves are called. However chess.com has shown it doesn't care what ECO calls openings and will push ahead with names anyone decides to try to call something. 

The ECO codes are more like the variation names at the top of the page in MCO. In the 2nd edition (1981) of ECO C, C68 has 20 lines. 5...Bd6 is lines 10 and 11, notes 56 to 67, referencing 20 games in the notes.

MCO and ECO work best for openings you don't know that much about. When you start your research on an opening, it's reasonable to add notes to the physical book, or to a separate notebook that parallels the physical book's layout. But once you have done significant research, you are better off creating your own detailed classification to make sense of the material.

My application: I was keeping notes of my own studies, and for teaching kids from the late 1980's through about 2005. At that time, I just liked to specify the MCO column as a matter of documentation dilligence. Now I'm getting active in chess again after a long hiatus, so I'm starting by revising my notes and lesson plans.

I appreciate all the info - I think any further questions would be off-topic for this thread - special thanks to Yetanotheraoc!