Well where should I start....lol Just thought the question was so timely since I just was given a Catalina Spa myself. Turns out that I did not know the model number of my spa either and searched the web for any info on the older unit and found very little on it. Not even from the Catalina site. It was apparently too old to even continue to admit they made it way back whenever. I did slowly dredge up some info on the unit though. Here is the web site for them: http://www.catalinaspas.com for what good that may do you. It was very little help to me as mine was not listed among the current models. Also found this: http://catalinaspapartsonline.com which may help you figure some things out. At least you may get some needed parts from there. I found some new filters and pump seals and cleaners for mine at spa depot which were priced better than Catalina parts were. They are here: http://www.spadepot.com/shop/?utm_source=TSD&utm_medium=homepagelogo&utm_campaign=1 My tub is about 10 or so years old and i had to replace the entire bottom wood structure of the tub support and rebbild the pumps. I have other things that I may have to address but have not filled it up yet and turned it on to see if other things are not working and if there is a leak...etc. Do you know how old the spa is? I found my model number from a website that used the model numbers to make a cover for the spa. You pick a brand and model and they have the template for that model on file. I sort of backed into it that way. Mine was sort of easy since there were not many choices for a spa with a TV and a Sound System with 4 speakers in the corners. You dont necessarily need the model number of the tub though. You will be better served knowing the model number of the various parts in the spa. Circuit board, heater, pumps, blower and whatever else. If the tub sat for any length of time you may have quite a bit of work to do. And maybe not. I was quite pleased to get mine for free and am learning that a free spa AIN'T FREE! lol But I went in with my eyes open looking forward to enjoying the challenge which it is turning out to be since this is my first spa and I come to this project knowing little about spas! At any rate the Catalina brand seems to be built as well as any of them and maybe better. If you post up a picture of it maybe someone could better help you. Did the owner state what the age of the spa was?