Technically, it's still YWWH, with the third 6 being only a part of the last letter. I would be inclined to say it was a mistake, but it's a pretty big one in that case - usually the literature has very little mistake in it (kudos to them, it's one thing they indeed do right, the proofreading).
About the triangle: indeed it's not unusual to represent the tetragrammaton inside a triangle, but afaik it's supposed to represent the trinity. For example in this article: http://estherhecht.wordpress.com/2010/09/28/a-santa-fe-mystery-the-tetragrammaton-in-the-triangle/ it says: "It is to be noted that the Tetragrammaton is enclosed in a triangle. In Europe, this was a common Christian symbol, denoting the One god of Moses and Abraham revealed in their New Covenant, as Three Divine Persons in one God . . . hence the Graeco-Latin term ‘Trinity.’".
Edit: also I have found this article quite interresting, the tetragrammaton inside a triangle, with the rays coming out of it is a freemason symbol: http://www.sacred-texts.com/mas/sof/sof26.htm
Overall I'd say it's quite a weird find... Isn't there a copyright note on the side? It might be the photo of the altar in Saint-Pierre the article was talking about.