The marking is likely RE 115. The 115 indicates the rail size that the anchor is designed to fit. The RE (Railway Engineering?) marking is often seen embossed on rail webs as part of the size and date markings. I believe it refers to a specific set of rail profile standards and measurements similar to those used by both the New Haven and the PRR on some, but not all rails and fittings. Just a way to be sure that each piece is intended to be used with others of the same design type. Following this line of thought, there may have been anchors marked NH 107 or PRR 119 for use with those particular rail profiles. Is it a bang-on or a wrench-on style?