A visibly obliquely ground Parker Vacumatic nib is most likely an Oblique variant, presumably OM. Gold nibs are individually ground in, which is why with a replacement only extensive test writing provides meaningful insights. Pocket-suitable models are basically all modern fountain pens, preferably not made of metal in order to avoid scratches from keys; as a smaller classic, the Montblanc Mozart 116 is suitable. Special grinds such as Italic Oblique or Fine Italic, e.g. via mrpen.co.uk, offer interesting options especially for tabular and mixed-script needs; further explanations can be found at nibs.com.