Your Zenith radio could very well have been one of the last American-made solid-state sets manufactured before the company's radio division left Chicago for Korea. Yours looks like an offshoot of the model that looked like a miniature console. I recently saw a picture of a set almost identical to yours on eBay; these don't turn up very often, but yours is living proof that there are still a few of them left.
The rattling speaker may be something as simple as a particle of dirt having gotten between it and the cabinet. Does the speaker rattle at all volume levels, or just at high volume?
I would try to repair the problem first before thinking about replacing the speaker, as these air-suspension speakers are or could be quite rare nowadays; I'm not sure if any of today's Korean, etc. radio manufacturers even use this type of speaker mounting arrangement anymore.
Your radio's model number and chassis number tag could be that little bit of paper that's showing behind the dial in your picture of the set.
IF strip on a PC board while the rest of the radio is hand wired? Hmmm.
Strange, IMHO. I would think that if Zenith went to the trouble of hand-wiring most of the set on a metal chassis, they would have done the entire set that way, including the IF amplifier stages. Somehow, I cannot imagine Zenith--even toward the end of their production of SS radios--doing something like that. After all, most of their older tube-type radios were 100-percent hand-wired on solid metal chassis; I didn't think they started using PC boards until at least the '80s, and they never, to the best of my knowledge, mixed PC boards and hand wiring, at least not until your set came along.