figured out the issue
First off, I want to thank everyone for their responses to my dilemma. The solution proved to be something very simple. Evidently, the previous owner had been fiddling with the internal safety lock and hadn't fully disengaged it. The head of the lock pin (item #53 in the expolded view in the instruction manual) was prodruding just far enough to catch on the frame when the main spring housing was swiveled outward, but was threaded in far enough to allow the pistol to function. Once the lock pin was threaded in all of the way, the gun disassembled without any further issues.
I think here might be a good place to give a word of caution. The manual states when one is reassembling the weapon to insert the magazine, pull the trigger with the muzzle pointing downward, and allow the hammer to fall forward in the fired, or decocked, position prior to attempting to latch the main spring housing. However I noticed on my sample the hammer will not fall on its' own without assistance. I investigated into why not, finding the magazine disconnector spring (item #37 in the manual) puts a very slight axial load on the hammer. The resulting drag is very slight, but enough to prevent the hammer from falling by gravity alone. Be careful! I hope this information helps others who may encounter disassembly/reassembly issues.
Again, I want to thank everyone for their suggestions.