Hi folks - have been enjoying reading your discussion! The gap between the portcullis and crossbar was a new one on me.
I started looking at microvarieties a month ago after finding Tony Clayton's website: http://www.coins-of-the-uk.co.uk/coins.html
You guys found 110, 113 and 109 beads around the reverse. Here's my 800+ pence-worth of observations on the obverses...
5 obverse border beading microvarieties on the 1p
Spink #B1: Second Portrait
1971, 73-76: 111 beads and first D points at bead
77-81: still 111 beads but first D points between beads
Sp#B2: Second Portrait, now "ONE PENNY"
1982-84: still 111 beads and first D points between beads
Sp#B3: Third Portrait
1985 only: 112 beads
1986-88: 109 beads
1989 only: 110 beads
1990-91: back to 109 beads
Sp#B4: Third Portrait, now copper-plated steel
1992-97: still 109 beads
Sp#B5: Fourth Portrait
1998-99: 115 beads
2000-08: back to 110 beads
I just gotta wonder why...!
Haven't found multiple varieties in a year - yet. Will be back with annotated photos and frequencies when I get a chance.
Cheers,
Sam