Actually, one (not uncommon) approach is to use a wire straddling the can into two through-holes. One can trust the mechanical contact, or if it is necessary to solder the wire to the can in addition, this can be done using a soldering iron with much less heat/ time.
the 'cans' are soldered together to prevent radiated signals from other places including adjacent crystals from affecting the signals being 'filtered'...
I hadn't read all the thread before I added my $0.02's worth
Crystals are cheap, engineering time isn't.
As a practical note, it should be firmly understood that 32768 Hz crystals are neither created equal, norclose. Crystal parameters vary widely between different models produced by the same manufacturer, orbetween manufacturers and styles of crystals. Designers must be aware that crystal oscillator circuits thatrequire ?tweaking? or that must have very high tolerance components to make the oscillator work aregoing to be marginal, at best. Most oscillators work reliably with components that vary over a reasonablerange of values. If a crystal is used that requires high-precision components, the circuit designer shouldgive very special consideration to using a different brand or style of crystal.
Low-frequency tuning elements are more sensitive to temperature than their high-frequency counterparts.In general, low-frequency crystals can be damaged more easily than high-frequency elements in solderingprocesses. Particular attention must be paid to keeping soldering operations within temperature ranges thatwill not damage the crystal. While high-temperature damage can manifest itself in many ways, the mostcommon symptom is the failure of the crystal to operate. Another way for temperature damage to expressitself is for the crystal to display bizarre or unexplainable start-up characteristics. If problems with a crystalsuddenly appear in a product line that previously had no problems, assembly soldering temperatures are agood place to investigate.