I have never been able to find a
good reference book on spear heads (the same holds true for arrows, cross-bow bolts and javelin heads). Instead you find them mentioned here and there in archeological or site reports. However, you have to be careful with these as not all of which are accurate when it
comes to dating a spear
head or two. If they don't have a specialist and aren't focussed on weaponry then they can end up citing erroneous information.
That said, the main outstanding characteristic that your spear
head has is the large thick ring at the base of the shaft. I have often seen this on spear heads identified as
medieval, and usually late
medieval. That does not mean that it can not be earlier just that
medieval is a possibility.
Shawn
