Old truss rods..Wrought iron?

I'm assessing an old historical building located in Canada which was built in 1902, and I was wondering if it's possible to visually tell if wrought iron was used in the tension rods in the queen post rod trusses shown below?

I reviewed an old 1908 pocket book "The Architect's and Builder's Pocket Book" by Kidder, which mentioned that truss rods are generally furnished in wrought iron unless steel is specified. (see below). The book also had a sketch of a truss very similar to what I'm looking at...which makes me think wrought iron was potentially used. Any thoughts on this? Thanks.