Could definitely be a Dufferin. The wood honestly looks like Morado which would make sense. Joey is correct in that it's 99.9% a house cue conversion. The full splice is flat-bottomed where the points meet the maple and honestly, if it looks like a duck, walks like a duck and quacks like a duck, it's probably not a velociraptor.
I truly believe it's 5/16-18" for the joints and is probably an early to mid-90's cue. The brown phenolic is really dark and the weave is pretty tight compared to the stuff we usually get now. I'm lucky to have an actual plastics distributor here.
The point is, you have $100 in it and it was probably a good buy just in and of itself. Plus you love the way it plays and haven't ever asked for a "value" (which is usually what causes arguments here.)
Wood is sometimes hard to really determine in pictures. For example, here is a 6 point coco I built late last year. The black streaks in it are somewhat different from what I see in your cue:
This is Morado from a Dufferin House Cue conversion I did:
This is a Rosewood sneaky I did from a fairly early Brunswick Tru-Balance. I put it in here because the rings you see at the bottom are modern rosewood and purpleheart. Notice the difference in the color and depth of the rosewood.
Lastly here is new brown phenolic vs what you have. Notice the grain on the new stuff is fairly loose and lighter in color.