This 1919 Shorpy photo that Ray1936 recently started a thread about got me thinking about the Alt Heidelberg and trying to detect whether the photo could reveal if the building still existed at that date. It can't, but it spurred me to google some more which turned up some new information.

According to a report from the Detroit City website, the Henry the Hatter building is indeed the same structure although remodeled around 1925-26. It's now called Standard Trust Company Building. There's mention of the architects of some of the buildings in the district, and at the end of the pdf there's a map of the buildings within it.

https://www.detroitmi.gov/LinkClick....=3096&mid=4357
Broadway+Avenue+Local+HD+Final+Report.pdf

Final Report
Proposed Broadway Avenue Local Historic District

pages 3 - 4
The assertively German Renaissance Abend Post Building, the home of August Marxhausen's German daily newspaper, built c. 1890 at the southeast comer of East Grand River, where the Merchants Building now stands, was the first large commercial building constructed along Broadway. It displayed a standing figure, presumably of Gutenberg, in a niche at the corner. Within the Gratiot-to-Grand River block of Broadway, the Cary and Breitmeyer [[Breitmeyer-Tobin) buildings, constructed in the 1905-07 period, were the next large commercial buildings. Another high, Flemish-gabled building next door to the Cary Building at 1307-9 Broadway soon followed, in 1907. It originally housed the Alt Heidelberg restaurant and buffet and the residence of its proprietor, Joseph H. Lume [[the North German or Low Country Renaissance façade was removed in 1925-26 in the renovation project that gave the facade its present character).

Little evidence of the first generation of smaller commercial buildings remains today because of subsequent renovations and enlargements and demolitions. The oldest of these buildings that retains a substantial part of its historic appearance is the Reckmeyer Building at 1326 Broadway, reconstructed in its present form c. 1896-97, the next oldest the 1911 J. Breitmeyer's Sons Building at 1310-14 Broadway.
...

A Detroit Free Press article in 1906 called Miami Avenue “the Broadway of Detroit” [[May 15, 1906). Miami Avenue was named after the Native American tribe; the name officially disappeared that year, replaced by Broadway to reflect Detroit’s growing theater district by associating it with that of New York City.

page 6
The block's other "German" Renaissance building, at 1307-09 Broadway, was built in 1907 for the Alt Heidelberg Restaurant. Occupied [[following the advent of Prohibition in 1920) by the Continental Bank beginning in 1921, it was entirely remodeled in 1925-26, probably for another bank, the Standard Trust Company, its brick front with Flemish gable transformed into a reserved limestone facade of vaguely classical inspiration. Not only the demands of commerce but also the public's hostility to all things German in the wake of World War I may have hastened the demise of these two assertively German landmarks.

page 14
1307-09 Broadway, Standard Trust Company Building
1907 [[Detroit building permit #1987, July 13, 1907); renovated 1912-13, 1925 [[alteration permits #1254-A, Oct. 4, 1912; #12947-A, Sept. 16, 1924; #22576-A, Dec. 8, 1925.
The Standard Trust Company Building is a limestone-clad, four-story commercial style commercial building. The facade above the street level is divided into two bays of tripartite windows. A metal with shallow brackets is topped by a solid balustrade with end and central piers and smaller piers aligned with the window dividers below. The top of a side-gabled tiled roof is visible above the parapet. The present storefronts may dated from the mid-1950s when Henry the Hatter moved into the southerly storefront. The building permits suggest that this building’s first two stories were constructed in 1907 and the upper two stories added in 1912-13 but a photograph of the street taken before the construction of the buildings at 1310-14 and 1322 Broadway, built 1911 and 1912, respectively) shows the building with its full four story facade. The original facade was of North German or Low Country Renaissance design and crowned above the 3rd story with a high Flemish gable. It was replaced with the current facade in 1925-26.