In reply to Oujmik:
Sorry about the confusion here. As Offwidth says, the text description in the CC Ogwen guide has the two routes in the correct order: as you approach along Heather Terrace from the right, Pinnacle Rib Route comes first, starting from the right side of the heather bay, and Overlapping Rib Route second, starting from the left side of the bay. The error is in the topo on page 114. The lines of the routes are correctly shown but the names are transposed. Sadly, despite much checking and rechecking, this is the sort of error that sometimes gets through the net when putting a guidebook together. This one was particularly annoying and I still kick myself whenever I think about it.
New visitors to the east face often have difficulty finding where routes start and the little schematic sketch on page 92 was included to help with this. Thankfully these two routes were shown in the correct order on it. Also 'Rib' is correct in both route names, not 'Ridge'.
The confusion with these two routes has a long history, and reverting to the original names in the Ogwen guide was an attempt to sort it out. The story goes that the alternative names – First Pinnacle Rib for Overlapping Rib Route, and Second Pinnacle Rib for Pinnacle Rib Route, became common in the 1930s, although they may have originated earlier than this. One plausible explanation I've heard for this is that if you were approaching on foot from the Pen y Pass Hotel (now the youth hostel) or the Pen y Gwryd Hotel, where most climbers stayed in the early days, you'd be coming in from the left and 1PR would be the first of the two routes to the Pinnacle that you reached, and 2PR the second. However, in later years when approaching from the Ogwen valley i.e. from the right, became the norm, this would be reversed and confusion has reigned ever since. Is that any clearer?
Anyway, apart from all that I hope you enjoy using the guide!