The D1 (D1-DF, 'Deep Face') was part of the Heavy Putter line built by Stephen Boccieri's company -- launched under the Heavy Putter name in 2005 and renamed Boccieri Golf in 2006 -- which pioneered mainstream counterbalanced putting: a head roughly twice the mass of a conventional putter (its flagship heavy-weight heads run near 900g versus ~500g standard) offset by an added weight plug in the grip end. The theory, echoed across golf instruction of the era, was that a heavier head paired with a counterbalanced grip end raises the putter's balance point, quieting handsy/wristy strokes in favor of a shoulder-driven pendulum motion. The D1 specifically used a deep-face mallet body to pair that counterbalance concept with extra face depth for a more forgiving strike profile.
Heavy Putter is credited by golf equipment media (LiveAbout's counterbalance history piece) as the original mainstream driver of counterbalanced putting technology, a concept later adopted industry-wide (SuperStroke, Odyssey Stroke Lab, etc.) -- it was influential on the category even though the specific D1 model itself never became a widely chased collectible.
Fits golfers who struggle with an inconsistent, hands-driven putting stroke and are willing to adapt to a much heavier feel through a learning period; not a fit for golfers who want a lightweight, feel-based blade putter or who are not willing to practice through the adjustment period reviewers describe as necessary before results improve.
Released in 2011 as part of Boccieri Golf's broader Heavy Putter DF (Deep Face) sub-line, competing with early counterbalance/heavy-head concepts before the mid-2010s counterbalanced-grip boom (SuperStroke, Odyssey Stroke Lab) made long, heavy grip counterbalancing mainstream; today's closest equivalent is any counterbalanced mallet with an oversized grip, e.g. Odyssey's Stroke Lab or Ping's PLD counterbalance options.
The deep-face mallet body and near-double head mass increase resistance to twisting on off-center hits versus a standard-weight putter, and the raised balance point is designed to reduce mis-hits caused by wristy strokes; it is not an extreme-MOI mallet like a modern max-stability design, so forgiveness sits in the middle of the category rather than at the top.
Calibrated across the whole catalog — a tour blade scores low here on purpose; it means control, not ease.
As an older (2011), niche-technology putter from a small manufacturer, used listings are limited; expect realistic private-party pricing in roughly the $40-$90 range, reflecting both its age and the fact that Heavy Putter/Boccieri never achieved mass secondary-market demand.
Reading is one thing — hitting is another. Book a bay and see the numbers for yourself before you buy anywhere.
