I think you mean a "Top-Break". "Tip-Up" is the common name for the early S&W's that had the hinge at the top of the frame and the barrel tipped "up" instead of down. (They didn't make any tip-ups in .38 caliber, only .22 and .32 RF)
That being said, there are a number of .38 top-breaks that the one you are asking about could be. Is it hammered or hammerless? Spur trigger or triggerguard? Single action or Double Action? Any chance for a picture?