Frankenstein Must Be Destroyed (1969)
There are three entries today because I somehow left out Frankenstein Must Be Destroyed in my original list. My lack of familiarity with Hammer is showing. I also skipped Frankenstein Created Woman, but that was more intentional since it's really more a Bride of Frankenstein story.
In the fourth Hammer Frankenstein film, Peter Cushing again plays the Baron. He's what ties the series together, not the Monster. It's a fascinating concept for a horror series, especially since Victor Frankenstein has always been the true monster of Mary Shelley's story. Having him chased across Europe from film to film as he continues his insane experiments is pretty brilliant.
This time around, he doesn't piece together a new monster so much as perform a brain transplant, but the results are about the same as most Frankenstein movies. Because of the change though, the Creature looked much less horrific than usual; really just a guy with a scar around the top of his head. The Dictionary of Hammer Horror has an excellent review of the film if you want to know more.
The Horror of Frankenstein (1970)
After Frankenstein Must Be Destroyed, Hammer decided to reboot the series with a new Victor (Ralph Bates instead of Peter Cushing). There was also a new Monster, but that was usual.
Well, I say it was a new Monster, but David Prowse had briefly played the Creature before in the James Bond spoof, Casino Royale. In fact, according to Wikipedia, he'd been lobbying to play a Hammer monster for years and finally got his break with this part. What's cool is that he would get to reprise the role in the next (and final) Hammer Frankenstein film, not only outlasting Horror of Frankenstein's new Victor (Cushing would take back the part of the Baron from Bates), but becoming the only actor to play the Monster twice in a Hammer film. But I'm getting ahead of myself.
Lady Frankenstein (1971)
Lady Frankenstein is the English-release title for Italy's La Figlia di Frankenstein (The Daughter of Frankenstein), a sort of What If version of the story in which the Baron is immediately killed by his Creature as soon as it comes to life. The Baron's daughter then takes over his work and sets to putting her elderly lover's brain into the younger, handsomer body of a mentally disabled fellow. Those Frankensteins are all bastards.
Which is why The Bad Movie Report interprets Lady Frankenstein as a sort of feminist work: "[I]n a bit of cinematic shorthand, even the most inexperienced of movie goers can say upon sight, 'Aha! Mad Scientist! Nothing good will come of this!' It is harder to leap to that conclusion when the character is female; a couple thousand years of cultural pressure informs us on a near-DNA level that women are to be protected (even, or perhaps especially, from themselves), and that they are more sensitive and in tune to life and nature's patterns and vibrations. Overcoming that stereotype would require some actual effort on the part of the filmmakers." Though it's an extremely flawed film, that effort alone - argues the Report - makes it feminist. I'm going to need to see it before I can agree or disagree; fortunately, I have a VHS copy lying around here somewhere.
As to the Monster's look, bald was sure popular between '69 and '71, with the Monster's head getting bigger every year. That was about to change, though I guess we could argue for a brief revival a few years later in Young Frankenstein.