I have a Castalla CN6N classical nylon string guitar. It was given to me new for Christmas (1969) by my mother (God rest her soul). I still have it and play it daily. It was a very inexpensive guitar but it has a very nice sound. I have since purchased A Takamine and Taylor Steel string guitars but I enjoy the easy play and tone of the old nylon.

Keep the thing in the case and with proper humidy and temp.

Note: You should NEVER put steel strings on a nylon/Classical guitar. The steel string guitars have a truss rod to keep the neck at the correct angle and a reinforced bridge where the nylon/Classical guitar doesn't. A nylon/Classical guitar also has an all wood bridge where the strings wrap around it and if you put steels on it they will cut into the wood and pretty much ruin the guitar. Also the tuning keys are friction based and the steels pull too hard and it make proper tuning difficult.