Can a magical rod, more specifically, the Rod of the Pact Keeper, double as a quarterstaff?
Rod of the Pact Keeper (DMG Pg. 197)
Rod, uncommon (+1), rare (+2), or very rare (+3) (requires attunement by a warlock)
While holding this rod, you gain a bonus to spell attack rolls and to the saving throw DCs of your warlock spells. The bonus is determined by the rod's rarity. In addition, you can regain one warlock spell slot as an action while holding the rod. You can't use this property again until you finish a long rest.
Most magical staves or rods specifiy whether or not the weapon can act as a magical quarterstaff, such as the Staff of Power.
Staff of Power (DMG Pg. 202)
This staff can be wielded as a magic quarterstaff that grants a +2 bonus to attack and damage rolls...
However, even if not specified, can it be argued that a rod, if used as an improvised weapon, may be utilized as a quarterstaff?
Improvised Weapon (PHB Pg. 147)
At the DM’s option, a character proficient with a weapon can use a similar object as if it were that weapon and use his or her proficiency bonus.
I realize it clearly states "At the DM's option", but I'm still curious to what the popular ruling may be, or if there is something around the web that may further support this argument.
Again, I realize I may simply work this out with my DM, but it is always nice to have some form of backing to these sort of things, such as a Sage Advice, a Tweet from J. Crawford, or some RAW or RAI to help build my case to the Dungeon Master or other players.