The leading assignee in this dataset holds 16 of the 149 records in scope, with a steep drop to 8 records at fifth place and 3 at tenth. That pattern — one clear leader followed by a long tail of smaller filers — means no single company controls the field outright, and the top holders show no filings in the most recent tracked year, so current leadership is more open than historical counts suggest. Anyone assessing freedom to operate should still check the leader's portfolio directly rather than assuming it is inactive.

Filings peaked at 29 records in 2021 and fell to 1 by 2024, a -97% change over that span. This kind of spike-then-drop pattern in a narrow geotechnical category often reflects a cluster of related filings — continuations, divisionals, or a coordinated portfolio build — around a specific technology window rather than a broad market pulling back. Note that publication lags filing by about 18 months, so 2025-2026 counts are still incomplete and should not be read as continued decline.

Force and pressure measurement (G01L), which covers proof-load testing instrumentation, appears in only 4.7% of the 149 records despite the search scope explicitly including proof load testing as a control point. Corrosion protection verification and grout body bond monitoring show similarly thin coverage relative to the 80.5% of records claiming core E02D foundation hardware. These gaps suggest verification and monitoring methods are claimed as afterthoughts within broader anchor patents rather than protected on their own terms.

E02D, foundations and earth drilling, is the dominant class, appearing in 80.5% of the 149 records in scope. E21D, shaft and tunnel support, follows at 23.5%, and E04C structural building components at 13.4%. Because a single record can carry multiple IPC classes, these figures do not sum to 100% and should be read as independent shares of the same 149-record base, not as parts of a whole.

US5423635A, granted to Paul Keller Ingenieurbuero AG, claims an anchoring element that allows corrosion-protection integrity checks on a ground anchor's protective tube by applying voltage across the strands and measuring current, even after grouting is complete. It is a specific verification method tied to particular hardware, not a broad claim over ground anchors generally. New filings that use different verification mechanisms, such as fibre-optic or acoustic monitoring instead of electrical continuity testing, would likely sit outside its claim scope, though a formal freedom-to-operate review is the only reliable way to confirm that.