Maybe these crucifixes belong to both churches in that they came into use before the Greek schism.
There is three ways to respond to this.
In evaluating a very old Crucifix, the manner in which Christ is represented is a good indication of the period and Tradition it belongs.
More on this here: http://www.shroud.com/pdfs/markwar3.pdf
The latin cross. The symbol of Christianity
The Orthodox cross. The upper bar represents the INRI sign and the lower slanted bar is a stylized foot stool.
For more symbols: http://altreligion.about.com/library/glossary/symbols/bldefslatincross.htm
The Art Tradition.
Byzantine and Orthodox: Characterized mostly by the stylized bulge at each 4 points.