Tom McGeeney's grandfather was Patrick Sylvester McGeeney, Sr. and his silent film production company was initially named Lone Star, and later, Shamrock Photoplays. In material on a subseqent webpage, there is mention of Primrose Pictures (in New York City) but that may have been a company owned by William Steiner (and perhaps it was a film distributor). Note the Lone Star stationary below which mentions studios/exteriors in San Jose and Terrell Wells in Texas as well as C. L. Nelson's Ranch in Mexico. McGeeney's film production companies were in operation from about 1915 - 1923.

Prolific western history researcher and writer Glenn Shirley (1916-2002) authored a biography on Tom's grandfather entitled Purple Sage (ISBN: 0935269045, Barbed Wire Press, June, 1989).

P. S. McGeeney was involved in A DEBTOR TO THE LAW (1919) which was based on the life of bandit and outlaw Henry Starr. Henry Starr was the star and Karl Hackett was also in the film. Tom McGeeney has some info that real Texas Rangers did some bit parts in A DEBTOR TO THE LAW.

P. S. McGeeney, Sr.'s other film work may include the following films:
HEART OF THE SUNSET (1918)
A DEBTOR TO THE LAW with Henry Starr circa 1919; there are posters showing Pan American Picture Corporation (which I believe was based in Muskogee, Oklahoma) presents A DEBTOR TO THE LAW
THE MASKED RIDER serial (Shamrock/Arrow, 1919)
LITTLE MISS BLUEBONNET (1922)
RANGELAND - Neal Hart/Benny Corbett western (Steiner, 1922)
PERILS OF THE WEST (Shamrock Photoplays/Primrose, 1922); the first of twelve two-reelers; unknown if any of the other films in the series were lensed; more on this film below.
THE GERM (1923)

  Although some of the data is incomplete or inaccurate, the Internet Movie Database (IMDB) has information on Patrick Sylvester McGeeney, Sr.: https://www.imdb.com/name/nm0569153/

THE MASKED RIDER chapterplay is currently being worked on by the Serial Squadron for release on DVD. Alas, the nitrate prints that they discovered are missing the credits. Marie Treador, who plays "Ma Chadwick" in this chapterplay, was the wife of William Steiner. More info at: http://www.serialsquadron.com/dvds/maskedriders/index.html

The Handbook of Texas Online is a project of the Texas State Historical Association. P. S. McGeeney is mentioned in their webpage on Texas film history: https://www.tshaonline.org/handbook/entries/film-industry

The portion on P. S. McGeeney is below (italics added to identify quoted text from the Handbook of Texas Online website):

"Other studios operated briefly in the San Antonio area. Patrick Sylvester McGeeney (lawman, Western genre novelist, and actor) organized the Lone Star Company on September 2, 1915, and produced several films. The company was abandoned briefly, then reorganized in May 1917 as the Shamrock Photoplay Corporation. It produced numerous feature films and serials, many of which achieved national distribution. Its production facilities were also leased to out-of-state companies conducting on-location shoots in San Antonio. Production ceased in early fall 1923."

You can read more about real life bandit and outlaw Henry Starr, including his death from gunshot wounds on February 22, 1921 which he suffered during a robbery attempt at a Harrison, Arkansas bank on February 18, 1921:
https://discover.hubpages.com/education/The-Outlaw-Henry-Starr
https://www.legendsofamerica.com/we-henrystarr/

Wm. K. Hackett in A DEBTOR TO THE LAW (1919)

(Courtesy of Thomas McGeeney) 1919 - several of the cast and crew from A DEBTOR TO THE LAW (Pan American, 1919). Real life bandit and outlaw Henry Starr is on the far left and was the star as well as an advisor. The man wearing the badge and carrying the Winchester is P. S. McGeeney, Sr. Hackett is on the far right, with moustache and decked out in the cowboy outfit. The two women and four men in the background are unidentified. The Vintage Posters website has a 1919 poster image for A DEBTOR TO THE LAW which seems to show Henry Starr and Hackett (with moustache and checkerboard shirt): http://www.vintageposters.com/catalog/hs1.html Blowup of Hackett's face from the image above. Blowup of the face of the man on the far right in the lobby card below. Compare the face, moustache and hair line in these two blowups - looks the same. (Courtesy of Thomas McGeeney) Above lobby card from A DEBTOR TO THE LAW (1919). Looks like our Carl Germain/Karl Hackett on the far right with the six-gun.

More on Patrick Sylvester McGeeney, Sr., and his Lone Star and Shamrock film companies.

(Courtesy of Thomas McGeeney) 1919 - Tom's grandfather P. S. McGeeney is center with the lever action, and the other two cast members are unidentified. This still is from A DEBTOR TO THE LAW and was used in a color poster for that film. (Courtesy of Thomas McGeeney) Above is letter head stationary from P. S. McGeeney's first film production company which he called Lone Star. A few years later, McGeeney's revised/re-formed film production company was named Shamrock Photoplays.

William Karl Hackett and wife - photos dated 1920 and 1921 from Dallas, Texas and Los Angeles.

(Courtesy of Thomas McGeeney) Above - Hackett and his wife. Salutation in the upper left reads: "To Mr. and Mrs. Mc Geeney with our best wishes   Both Hacketts   8/5/20". Photographic studio info in lower left shows the name "Mahoney" and Dallas, Texas. If Hackett was married only once, his wife would be Ruby Moore Germain. And in the 1920s, when Hackett was doing stage plays and vaudeville and had his "Hackett's Players" company, one of the members was Ruby Moore. (Courtesy of Thomas McGeeney) Above - Hackett at about 28 years of age. Salutation in the upper left reads: "To my friend McGeeney With best wishes". Signature and info in the lower right reads: "Wm Karl Hackett   3/4/21   Los Angeles California". Photographic studio info in lower right shows the name "Kohler" over an "LA" (short for Los Angeles?). Why would Hackett send portrait stills to Patrick Sylvester McGeeney, Sr.? Seems pretty obvious - he probably knew that McGeeney was thinking about doing some new films, and Hackett wanted to keep his name in front of the Shamrock production company boss.