It's certainly not th usual 14th/15thC sallet style helm you see, with a suggestion of a nasal remnant. That said, the swirl effect was popular in italy/spain in the late 1400s, early 1500s, so it's possible you could consider it a spanish import, which certainly was popular with the Irish here. If you were going for a 'low-status late gallowglass, AKA pikeman', I'd say it's acceptable.
John, a 14/15thC sallet...? Surely you mean bascinet? Also if this helmet is to be regarded as a Spanish import then why would you regard it as been particularly suitable for a 'low-status late gallowglass'? I see no reason to regard a Spanish import as having been of any lesser quality - and certainly not any lesser cost - than its domestic (not any real evidence for this as of yet) or its British counterpart. If anything, an imported helm of this type would have to be regarded as a high-status item.
Finn, first up, from what I know of bascinets (not a vast amount as I'm really a sixteenth-century specialist) the type you have there is of early type and appears to conform to the period in and around the first quarter of the fourteenth century - its shallow back and sides are an indication of this (c/f colour plate commentary: Osprey Warrior 124 'Teutonic Knight' p.61, Plate D, No.10). By way of qualification, the eight fifteenth-century galloglas on the earlier thirteenth-century O'Connor tomb at Roscommon Abbey appear to be wearing a far deeper, and therefore later, type of bascinet. Secondly, as John has remarked, the ridged swirl effect is an indication that the helmet is most likely of Mediterranean origin which in the hands of a galloglass could mean either it was imported (at some expense as stated above) or was lost and found in the field of battle, still quite unlikely - although not entirely impossible - in the Irish context. Incidentally, the only bascinet to be yielded thus far on the Irish archaeological record is, unsurprisingly, of the plain (i.e. no ridged swirls) finish type.
Because of the first reason (and allowing a buffer of three-quarters of a century to allow for Gaelic-Irish 'conservatism') I would be inclined not to use it for fifteenth-century interpretations but only for fourteenth and possibly late thirteenth-century events. For the second reason - I would be inclined not to use it at all - simply because I feel that it would not be typical, or at least not typical enough of the period in galloglas hands. That's just my opinion by the way!
Btw Finn - from the picture you have supplied the helmet appears to well-made/finished.
Have a good weekend people.