[Ron Wood]

Let me see if I can "horsey-duckie" this situation.
1) You can own as many stocks as you wish if you have no guns to which they may be attached.
2) You may own any original or close copy reproduction stock if you have a corresponding Luger to go with it. This is a one for one basis, i.e. you can't own 3 LP08 stocks with only one LP08 to go with them if you own other short barreled Lugers to which the extra two stocks could be affixed. That is why I got rid of my repro Navy stock when I acquired an original since I own only one Navy Luger. I wouldn't worry too much about this one for one restriction...I doubt that it would be too much of an issue as long as you owned at least one legitimate corresponding Luger. Collectors tend to accumulate "spares" or trading material so there may be some leeway on this issue.
3) You may not own any stocks for which you have no corresponding model Lugers, but you do own short barreled Lugers. Note that this an important distinction and negates the assertion that "it is perfectly legal and NOT an issue to own a artillery stock without an artillery".

The "constructive intent" issue may not be rigidly enforced but it is always there and can be used against anyone who is in violation of the above 3 conditions.