Hello and Welcome to the Forum, we have a lot of great folks here, and possibly some one can help you better than I can, but for now this is where and I how I think you should start.
I saw your question listed last week on Highroad and you apparently did as Gus suggested and called the company. Actually the company you should have checked with is the parent company CZUB, and even then it may not do you much good, since BRNO was at one time a completely separate entity that CZUB as we know it today acquired it. I would try e-mailing CZUB give them year, make and model of the rifle, sending pictures may help a lot, Also do not forget the serial number. Forget phoning. Well actually you could try phoning but you may end up getting shuffled around between divisions, and calling the Czech Republic isn't going to be inexpensive or a walk in the park either.
You didn't happen to mention whom you acquired the rifle from, the estate itself, or someone that had bought it from the estate and then turned around and sold it to you. Oh and that's fine, no need to go into those details really, I think possibly that is not anything we need to know. However, what I'm getting at is, trying contacting the Estate, family or friends and see if any of them remember anything about that weapon. I would also strongly advise you to actually write (word process) print sign and send USPS, And on nice paper if possible. When you are dealing with old money, (and trust me you are dealing with money and maybe only 1930's or 40's old but different times etc.) you need to approach them slightly more formally then but e-mail which more than likely wouldn't get past their fire walls certainly not a secretary. A letter might get further and do more. Feel free to have you e-mail address as part of your letterhead, that way if they choose to contact you they may well do so that way, BUT the first move is yours and a written signed letter carries weight and courtesy which may well turn the tide on a response in your favor.
Oh Ya and also check with the NRA Museum, They apparently got a goodly portion of the gentleman's weapons collection, and may well know exactly what you are talking about. Or whom you might contact regarding it. They have always been very helpful when I have had questions.