Unquestionably post 2004 Taylor Schrade or BTI Schrade Chinese manufacture.
1) Tang Stamp.
1956 to 1988 Manufacture has "PROV. RI. USA" on the tang stamp. 1988 to 2004 has the "Imperial Ireland" tang stamp. Production of all Imperial knives was moved to Ireland after the Providence, R.I. plant burned down in 1988. Apparently it cost less up front to purchase an established knife manufacturer in Ireland than to rebuild the R.I. plant.
Secondary costs, however were much greater. For some reason customers believed the knives made in Ireland were somehow inferior to the made in USA knives (they weren't/aren't), so Imperial sales dropped significantly.
Who knows? Perhaps if Imperial Schrade had rebuilt the R.I. plant, the bankruptcy would have been delayed, or not have happened at all?
2) The "biggie": Stainless steel blades.
ALL the Imperial Schrade USA produced shell construction knives (includes the 1988-2004 Ireland knives) have 1095 Carbon Steel blades. I'm pretty sure none of the Imperial knives had stainless steel blades until after the bankruptcy and production of Imperial knives was moved from Ireland to China.
EDIT:
I believe the use of stainless blades on the post 2004 Imperial and Old Timer lines is one of the Taylor/BTI anti fraud changes to prevent dishonest sellers from passing off a post bankruptcy offshore produced knife as a collector desirable Made in USA (and in the case of Imperial, the somewhat less desirable Ireland knives.)