Hi ya gdk! Welcome to ALR. You are in the right place.
While today's parts suppliers offer I. Haines furniture in iron (steel), the originals would have been mounted with brass furniture. I just checked RCA II and the 4 I. Haines guns (2 attributed, 2 signed), all are brass mounted and do not have any forestock, checkpiece or thumb piece inlays.
But as Dane says, do what makes you happy. BTW.... my I. Haines has iron furniture... wink.
-Ron