seems like a fancy name for a shirt to me .......how would I spot one of these miraculous garments
There are short and long sleeve. The classy long sleeve models (called Guayabera in the DR) will have the old style flip over cuffs.
Only in the DR have I seen that they'd call only long sleeve versions "Guayabera" and the short sleeve version Chacabana. Cubans and most South Americans refer to the short sleeved version or both as Guayabera.
Guayabera can be worn at high class social gatherings, paired with white or black slacks and quality matching shoes. A quality hat and maybe some gold here and there. A quality Guayabera can easily cost USD 200.oo and up at fine gentlemen's boutiques in major cities of Latin America.
The key is quality. So, you want to be extra careful whom you buy from:
'Cause if you happen to be taken for the fake stuff, you may soon find yourself surrounded by folk who prefer to wear nothing at all.
and will never look like the real deal:

... J-D.