first, that's at least an 1985, probably a 1986, and definitely not an '84. these second-generation allez bikes are blue; earlier bikes are red.
second, jim merz can confirm this but i'm 99.9% sure that the seller is correct in id'ing this as a miyata. it's basically the same frame as its predecessor the allez SE, but with shimano "new 600" parts instead of the suntour/specialized mix that came on the SE.
the production volume of these bikes precludes their being hand built. the merz signature sticker says 'designed by', not 'built by'. some earlier allez's (pardon my grammar) had a similar 'designed by tim neenan' sticker. but some didn't.
cheers, randy dugan van nuys, ca usa
Vintage 1984 Specialized Allez Road Bike Bicycle Clean!
On rear non drive stay Jim Merz has his named siged.
So is this 52 C Japanese Lugged Beauty...or built by CR Member Jim Mrez
Walnut Creek, CA USA eBay Item number: 220359907940