Hydrino, H(1/p), is any small form of atomic hydrogen with state energy E n = -13.598/n 2 eV, in which n = 1/p, and p is a limited integer 1 < p ≤ 137. Electron transition to a hydrino state is non-radiative and requires a quantized amount of energy, 2mE1 (m is integer) to be transferred to a catalyst. Furthermore, hydrino can dimerize to molecular hydrino, H 2 (1/p), by loss of its bond energy, e.g., to a reaction wall. In contrast to molecular hydrogen, molecular hydrino is paramagnetic with S = 1/2. We have previously reported a uniquely sharp multi-line EPR spectrum for gaseous molecular hydrino included in spheres of gallium oxide hydroxide, H 2 (1/4)@Ga(O)OH, which was produced in a plasma discharge reactor with gallium as an electrode and nascent water as the catalyst. Contrarily, EPR spectra of a very different nature are exhibited by H 2 (1/4) produced in multiple reactors of different type. Broad-line powder patterns are observed extending from 0 to some 8000 Gauss in dual-mode X-band. Unusual temperature dependence includes anti-Curie behaviour and a magnetic phase transition around 107 K. Frequency-dependent resonance conditions are identified in L-, S-, X-, and Q-band. The broad EPR is analyzed in terms of a temperature-dependent dimer-of-dimers to dimer equilibrium of molecular hydrino interstitially included in the microcrystals of powder hosts. The room-temperature EPR provides a simple fingerprint identification tool to monitor the production of molecular hydrino in stable catchers.